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From Smithsonian/NASA ADS Astronomy/Planetary Abstract Service
Title: Mapping using the Tsyganenko long magnetospheric
model and its relationship to Viking auroral images
Authors: Elphinstone, R. D.; Hearn, D.; Murphree, J. S.;
Cogger, L. L.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(Calgary, University, Canada)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 96, Feb. 1, 1991, p. 1467-1480. Research
supported by NSERC. (JGR Homepage)
Publication Date: 02/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, CURRENT DENSITY, EARTH MAGNETOSPHERE,
GEOMAGNETIC TAIL, SATELLITE IMAGERY, ATMOSPHERIC
MODELS, ULTRAVIOLET RADIATION, VIKING SPACECRAFT
Bibliographic Code: 1991JGR....96.1467E
Abstract
The Tsyganenko long magnetospheric model (1987) has been used in
conjunction with ultraviolet images taken by the Viking spacecraft to
investigate the relationship of the auroral distribution to different
magnetospheric regions. The model describes the large-scale structure
of the magnetosphere reasonably well for dipole tilt angles near zero,
but it appears to break down at higher tilt angles. Even so, a wide
variety of auroral configurations can be accurately described by the
model. It appears that the open-closed field line boundary is a poor
indicator of auroral arc systems with the possible exception of
high-latitude polar arcs. The auroral distribution typically called the
'oval' maps to a region in the equatorial plane quite close to the
earth and can be approximately located by mapping the model current
density maximum from the equatorial plane into the ionosphere. Although
the model may break down along the flanks of the magnetotail, the
large-scale auroral distribution generally reflects variations in the
near-earth region and can be modeled quite effectively.
Title: The configuration of the auroral distribution for
interplanetary magnetic field Bz northward. I - IMF
Bx and By dependencies as observed by the Viking
satellite
Authors: Elphinstone, R. D.; Jankowska, K.; Murphree, J. S.;
Cogger, L. L.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(Calgary, University, Canada)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 95, May 1, 1990, p. 5791-5804. Research
supported by NSERC. (JGR Homepage)
Publication Date: 05/1990
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ZONES, INTERPLANETARY MAGNETIC FIELDS,
MAGNETIC FIELD CONFIGURATIONS, SATELLITE IMAGERY,
AZIMUTH, SPATIAL DISTRIBUTION, TEMPORAL
DISTRIBUTION, VIKING SPACECRAFT
Bibliographic Code: 1990JGR....95.5791E
Abstract
Viking images obtained throughout 1986 have been utilized in
combination with IMP 8 satellite measurements of the IMF to determine
typical Northern Hemisphere auroral distributions for a variety of IMF
Bz positive conditions. Varying By has an effect which is consistent
with expected results; that is, By positive implies high-latitude
auroral arcs in the dusk sector, while negative By gives dawn-sector
polar arcs. A new result gives significant importance to the Bx
component of the IMF. Bx toward the sun gives polar arcs on both dawn
and dusk with comparatively weak UV emissions. With Bx away from the
sun, a single sun-aligned morning-sector polar arc dominates the
auroral distribution.
Title: Temporal and latitudinal 5577 A airglow variations
Authors: Cogger, L. L.; Elphinstone, R. D.; Murphree, J. S.
Affiliation: AA(Calgary, University, Calgary, Alberta, Canada),
AB(Calgary, University, Calgary, Alberta, Canada),
AC(Calgary, University, Calgary, Alberta, Canada)
Journal: Canadian Journal of Physics, vol. 59, Oct. 1981, p.
1296-1307. Natural Sciences and Engineering Research
Council of Canada
Publication Date: 10/1981
Category: Geophysics
Origin: STI
NASA/STI Keywords: AIRGLOW, ANNUAL VARIATIONS, HARMONIC ANALYSIS, ISIS
SATELLITES, LATITUDE, OXYGEN SPECTRA, EQUINOXES,
OXYGEN ATOMS, REMOTE SENSING, SOLSTICES, SPECTRUM
ANALYSIS
Bibliographic Code: 1981CaJPh..59.1296C
Abstract
>From 32,000 forbidden O I 577 A airglow limb observations made
between April 1971 and December 1972 from the ISIS-2 satellite, the
major temporal and spatial night airglow features have been identified.
Two methods of analysis were employed: harmonic fitting and global
correlation. Airglow emission rate maxima occurred in mid-October and
mid-April at all latitudes. The intensities peaked near 35 deg in the
winter and near 25 deg in the summer, and showed a symmetry with
latitude centered about 5 deg in the winter hemisphere. The mean
intensity at mid-latitudes was 175 R, and near the equator was 120 R.
>From the global correlation analysis it was shown that there are
two distinct contributions to the temporal and spatial airglow
variations: one is from local production, which dominates during the
post-solstice period, and the other is from large scale meridional
transport, which dominates during the post-equinox period.
Title: What is a global auroral substorm?
Authors: Elphinstone, R. D.; Murphree, J. S.; Cogger, L. L.
Journal: Reviews of Geophysics, Volume 34, Issue 2, p.
169-232 (RvGeo Homepage)
Publication Date: 00/1996
Origin: AGU
AGU Keywords: Magnetospheric Physics: Auroral phenomena,
Ionosphere: Ionosphere/magnetosphere interactions,
Ionosphere: Particle precipitation
Abstract Copyright: (c) 1996: American Geophysical Union
DOI: 10.1029/96RG00483
Bibliographic Code: 1996RvGeo..34..169E
Abstract
The departure of the aurora from quiet levels in a dynamic manner
constitutes some type of auroral ``breakup'' event. Research into the
auroral breakup predates the International Geophysical Year
(1957/1958). This feature of the aurora, and the later, more global
concept of the auroral substorm, has become a focus for much of the
auroral research that occurs today. New instrumentation and global
collaborations continue to refine our knowledge of the substorm process
and how it proceeds in the ionosphere. In particular, global auroral
imaging has advanced our understanding of the dynamics of the process
and has given us the ability to put localized observations into a
global perspective. Fundamentally new cycles of auroral activity are
now understood to exist, and this has provided a means by which auroral
activity can answer questions about magnetospheric substorm dynamics.
Along with this wealth of observations has come a wide range of
theories purporting to explain the mechanism of the onset of this
phenomenon. There is, however, no single theory which stands out as
clearly explaining the wide range of active auroral phenomena. A
synthesis which combines these theories and allows them to each explain
individual aspects of the problem appears to be required. This has led
to a new way of understanding the active aurora as a set of processes
or modules which occur either coupled together or independent of one
another to form a particular event. This view represents a fundamental
departure from the view of the substorm as a single unchanging entity.
Auroral activity can rather be thought of as the earthward end of a
diverse set of ionospheric and magnetospheric processes which couple
together to form different cyclical patterns. A symbolic representation
of this modularization is presented to simplify future schematics of
large-scale auroral dynamics.
Title: Global numerical simulation of the growth phase and
the expansion onset for a substorm observed by
Viking
Authors: Fedder, J. A.; Slinker, S. P.; Lyon, J. G.;
Elphinstone, R. D.
Journal: Journal of Geophysical Research, Volume 100, Issue
A10, p. 19083-19094 (JGR Homepage)
Publication Date: 10/1995
Origin: AGU
AGU Keywords: Magnetospheric Physics: Solar wind/magnetosphere
interactions, Magnetospheric Physics: Storms and
substorms, Magnetospheric Physics: Auroral
phenomena, Magnetospheric Physics: Numerical
modeling
DOI: 10.1029/95JA01524
Bibliographic Code: 1995JGR...10019083F
Abstract
We report the first global magnetohydrodynamic (MHD) simulation of an
actual magnetospheric substorm, which has recorded by the Viking
spacecraft on October 19, 1986. The simulation is driven by IMP 8 solar
wind parameters measured upstream of the Earth's bow shock. The
substorm, which had expansion onset at 1132 UT, was caused by a brief
period of southward interplanetary magnetic field (IMF) and two weak
solar wind shocks. The simulation model includes a self-consistent
auroral ionospheric conductance depending directly on the MHD
magnetospheric plasma parameters and magnetic field. Synthetic auroral
emissions, derived from simulation results, are compared to the Viking
images, which show considerable dayside activity preceding the
substorm. We also compare model-derived synthetic AU and AL indices to
geomagnetic measurements. The simulation results are seen to be in
resonable agreement with the observations throughout the growth phase
and expansion onset. Moreover, the results allow us to form conclusions
concerning which essential processes were responsible for the substorm
occurrence. These results are a highly encouraging first step leading
toward development of a space weather forecasting methodology based on
the directly measured solar input. .
Title: Large-scale high-latitude dayside auroral emissions
Authors: Murphree, J. S.; Elphinstone, R. D.; Hearn, D.;
Cogger, L. L.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(Calgary, University, Canada)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 95, March 1, 1990, p. 2345-2354. Research
supported by NSERC. (JGR Homepage)
Publication Date: 03/1990
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, DAYGLOW, GEOMAGNETIC TAIL, INTERPLANETARY
MAGNETIC FIELDS, ULTRAVIOLET RADIATION, FLUX
TRANSFER EVENTS, KELVIN-HELMHOLTZ INSTABILITY,
MAGNETOSHEATH, POLAR REGIONS, TEMPORAL DISTRIBUTION
Bibliographic Code: 1990JGR....95.2345M
Abstract
Observations made with the Viking UV imager reveal that on the dayside
of the auroral distribution there often occur emission features
poleward of the normal continuous auroral distribution when the IMF is
northward and in an away garden hose configuration. The position of
these features, the strong IMF dependence, and the observation that
large-scale polar arcs are seen to frequently connect to these dayside
features suggest that these auroral emission features are the result of
processes occurring on the front surface of the magnetotail. This is
consistent with the discovery that these features seem to exist
predominantly when the IMF B(y) component is positive, B(x) negative,
and B(z) is northward, which implies that merging on the front surface
of the magnetotail is involved in producing these emissions. Evidence
is presented which distinctly links the location of merging lines due
to dipole tilt and magnetic activity with the location of this
high-latitude dayside features.
Title: Modeling the growth phase of a substorm using the
Tsyganenko model and multi-spacecraft observations -
CDAW-9
Authors: Pulkkinen, T. I.; Baker, D. N.; Fairfield, D. H.;
Pellinen, R. J.; Murphree, J. S.; Elphinstone, R. D.;
McPherron, R. L.; Fennell, J. F.; Lopez, R. E.;
Nagai, T.
Affiliation: AA(NASA, Goddard Space Flight Center, Greenbelt, MD;
Finnish Meteorological Institute, Helsinki,
Finland), AB(NASA, Goddard Space Flight Center,
Greenbelt, MD), AC(NASA, Goddard Space Flight
Center, Greenbelt, MD), AD(Finnish Meteorological
Institute, Helsinki, Finland), AE(Calgary,
University, Canada), AF(Calgary, University,
Canada), AG(California, University, Los Angeles),
AH(Aerospace Corp., El Segundo, CA), AI(Applied
Research Corp., Landover, MD), AJ(Meteorological
Research Institute, Tsukuba, Japan)
Journal: Geophysical Research Letters (ISSN 0094-8276), vol.
18, Nov. 1991, p. 1963-1966. Research supported by
NASA. (GeoRL Homepage)
Publication Date: 11/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: GEOMAGNETIC TAIL, GEOMAGNETISM, IONOSPHERIC
CURRENTS, MAGNETIC FIELDS, MAGNETIC STORMS,
SATELLITE IMAGERY, CURRENT SHEETS, TEMPORAL
DISTRIBUTION, ULTRAVIOLET RADIATION, VIKING
SPACECRAFT
Bibliographic Code: 1991GeoRL..18.1963P
Abstract
The CDAW-9 Event C focused upon the early part of 3 May 1986 when a
large substorm onset occurred at 0111 UT. By modifying the Tsyganenko
1989 magnetic field model, a model is constructed in which the
near-earth current systems are enhanced with time to describe the
observed development of the tail magnetic field during the growth
phase. The cross-tail current intensity and the thickness of the
current sheet are determined by comparison with three spacecraft in the
near-earth tail. The location of the auroral bulge as recorded by the
Viking imager is mapped to the equatorial current sheet. The degree of
chaotization of the thermal electrons is estimated, and the
consequences to the tail stability towards on tearing are discussed. It
is concluded that the mapping of the brightening region in the auroral
oval corresponds to the regions in the tail where the current sheet may
be unstable towards ion tearing.
Title: Configuration of the auroral distribution for
interplanetary magnetic field Bz northward. II -
Ionospheric convection consistent with Viking
observations
Authors: Jankowska, K.; Elphinstone, R. D.; Murphree, J. S.;
Cogger, L. L.; Hearn, D.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(Calgary, University, Canada),
AE(Calgary, University, Canada)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 95, May 1, 1990, p. 5805-5816. Research
supported by NSERC. (JGR Homepage)
Publication Date: 05/1990
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ZONES, BIRKELAND CURRENTS, CONVECTION
CURRENTS, EARTH IONOSPHERE, INTERPLANETARY MAGNETIC
FIELDS, SATELLITE OBSERVATION, AZIMUTH, FIELD
ALIGNED CURRENTS, NORTHERN HEMISPHERE, POLAR
REGIONS, SPATIAL DISTRIBUTION, VIKING SPACECRAFT
Bibliographic Code: 1990JGR....95.5805J
Abstract
Views of the northern hemisphere auroral distribution obtained by the
Viking satellite present a qualitative means of inferring the
convective patterns which occur during IMF B(z) northward. The approach
is taken whereby upward field-aligned currents are assumed to be
coincident with large-scale discrete auroral features and on this basis
possible convective patterns are deduced. While the patterns are not
unique solutions, they are found to be consistent with merging theory
predictions: for B(z) northward, the auroral observations support the
possibility of three and/or four cell patterns. When the IMF azimuthal
angle is 90 deg (270 deg), a clockwise (anticlockwise) cell is found to
be located in the polar region between the two standard viscous cells.
When IMF B(x) dominates and is in a toward orientation, convection
stagnates, whereas if B(x) is negative, a four-cell pattern may form
with sunward flow at very high latitudes.
Title: CDAW 9 analysis of magnetospheric events on May 3,
1986 - Event C
Authors: Baker, D. N.; Pulkkinen, T. I.; McPherron, R. L.;
Craven, J. D.; Frank, L. A.; Elphinstone, R. D.;
Murphree, J. S.; Fennell, J. F.; Lopez, R. E.;
Nagai, T.
Affiliation: AA(NASA, Goddard Space Flight Center, Greenbelt,
MD), AB(NASA, Goddard Space Flight Center,
Greenbelt, MD; Finnish Meteorological Inst.,
Helsinki, Finland), AC(NASA, Goddard Space Flight
Center, Greenbelt, MD; California Univ., Los
Angeles), AD(Alaska Univ., Fairbanks, AK), AE(Iowa
Univ., Iowa City), AF(Calgary Univ., Canada),
AG(Calgary Univ., Canada), AH(Aerospace Corp., El
Segundo, CA), AI(Maryland Univ., College Park),
AJ(Meteorological Research Inst., Ibaraki, Japan)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 98, no. A3, p. 3815-3834. (JGR Homepage)
Publication Date: 03/1993
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, MAGNETOSPHERIC INSTABILITY, POLAR
SUBSTORMS, DYNAMICS EXPLORER 1 SATELLITE, HIGH
TEMPERATURE PLASMAS, MAGNETIC SIGNATURES, SOLAR WIND
Bibliographic Code: 1993JGR....98.3815B
Abstract
An intense geomagnetic substorm event on May 3, 1986, occurring toward
the end of a strong storm period, is studied. The auroral electrojet
indices and global imaging data from both the Northern and Southern
Hemispheres clearly revealed the growth phase and expansion phase
development for a substorm with an onset at 0111 UT. An ideally located
constellation of four spacecraft allowed detailed observation of the
substorm growth phase in the near-tail region. A realistic
time-evolving magnetic field model provided a global representation of
the field configuration throughout the growth and early expansion phase
of the substorm. Evidence of a narrowly localized substorm onset region
in the near-earth tail is found. This region spread rapidly eastward
and poleward after the 0111 UT onset. The results are consistent with a
model of late growth phase formation of a magnetic neutral line. This
reconnection region caused plasma sheet current diversion before the
substorm onset and eventually led to cross-tail current disruption at
the time of the substorm onset.
Title: The auroral distribution and its relation to
magnetospheric processes
Authors: Elphinstone, R. D.; Hearn, D. J.
Affiliation: Department of Physics and Astronomy, University of
Calgary, 2500 University Drive N.W., Calgary, AB,
T2N 1N4, Canada
Journal: Advances in Space Research, Volume 13, Issue 4, p.
17-27. (AdSpR Homepage)
Publication Date: 04/1993
Origin: ELSEVIER
Abstract Copyright: (c) 1993 Elsevier Science B.V. All rights reserved.
DOI: 10.1016/0273-1177(93)90306-V
Bibliographic Code: 1993AdSpR..13...17E
Abstract
The auroral distribution has several aspects which can be naturally
related to magnetospheric processes. Dayside asymmetries in intensity
and location of emissions enable one to visualize the implied
convection and thus the geometry of dayside boundary regions. For By
> 0 (By < 0) northern hemisphere polar arcs tend to be
confined to the dusk (dawn) sector and the dusk (dawn) auroral
distribution tends to lie poleward of the dawn (dusk) emissions near
noon. These observations are consistent with the orientation of the
convection throat and its dependence on IMF By. High
latitude dayside features, poleward of the particle cusp, are also
dependent on By and confirm that there is indeed a separate
auroral system (and presumably current system) in the particle plasma
mantle region (as defined by DMSP). The distribution of the auroras in
the midnight sector during both quiet and disturbed times allows one to
make important inferences about the mapping of these forms into the
magnetotail. Fundamental to this is the observations of a continuous
oval throughout the night sector, the location of substorm onset
relative to this oval and the subsequent development of a ``double
oval'' during substorm recovery. A unique set of observations are given
illustrating how the different portions of the ``double oval'' develop
during a substorm expansion phase. These observations support the view
that on some occasions the expansion phase dominantly affects the
central plasma sheet and leaves the inner and outer edges of the
magnetotail relatively undisturbed. New observations concerning the
dynamics of arc development westward of the auroral surge supports an
hypothesis of Alfven waves modulating currents which in turn give rise
to magnetic pulsations and multiple auroral arc systems.
Title: Dynamics of the lower thermosphere consistent with
satellite observations of 5577 Šairglow: II. Atomic
oxygen, local turbulence, and global circulation
results
Authors: Elphinstone, R. D.; Murphree, J. S.; Cogger, L. L.
Journal: Canadian Journal of Physics. Vol. 62, p.382
Publication Date: 00/1984
Origin: ADS
Bibliographic Code: 1984CaJPh..62..382E
Abstract
Not Available
Title: On open and closed field line regions in
Tsyganenko's field model and their possible
associations with horse collar auroras
Authors: Birn, J.; Hones, E. W., Jr.; Craven, J. D.; Frank, L. A.;
Elphinstone, R. D.; Stern, D. P.
Affiliation: AA(Los Alamos National Laboratory, NM), AB(Los
Alamos National Laboratory, NM), AC(Iowa,
University, Iowa City), AD(Iowa, University, Iowa
City), AE(Calgary, University, Canada), AF(NASA,
Goddard Space Flight Center, Greenbelt, MD)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 96, March 1, 1991, p. 3811-3817. DOE-supported
research. (JGR Homepage)
Publication Date: 03/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: ASTRONOMICAL MODELS, AURORAS, INTERPLANETARY
MAGNETIC FIELDS, MAGNETIC FLUX, PLANETARY
MAGNETOSPHERES, FIELD ALIGNED CURRENTS,
MAGNETOPAUSE, MAGNETOTAILS, POLAR CAPS, POLAR
REGIONS, SATELLITE IMAGERY
Bibliographic Code: 1991JGR....96.3811B
Abstract
The boundary between open and closed field lines is investigated in the
empirical Tsyganenko (1987) magnetic field model. All field lines
extending to distances beyond -70 R(E), the tailward velocity limit of
the Tsyganenko model are defined as open, while all other field lines,
which cross the equatorial plane earthward of -70 R(E) and are
connected with the earth at both ends, are assumed closed. It is found
that this boundary at the surface of the earth, identified as the polar
cap boundary, can exhibit the arrowhead shape, pointed toward the sun,
which is found in horse collar auroras. For increasing activity levels,
the polar cap increases in area and becomes rounder, so that the
arrowhead shape is less pronounced. The presence of a net B(y)
component can also lead to considerable rounding of the open flux
region. The arrowhead shape is found to be closely associated with the
increase of B(z) from the midnight region to the flanks of the tail,
consistent with a similar increase of the plasma sheet thickness.
Title: Observations in the vicinity of substorm onset:
Implications for the substrom process
Authors: Elphinstone, R. D.; Hearn, D. J.; Cogger, L. L.;
Murphree, J. S.; Singer, H.; Sergeev, V.; Mursula, K.;
Klumpar, D. M.; Reeves, G. D.; Johnson, M.
Affiliation: AA(University of Calgary, Calgary, Alberta, Canada),
AB(University of Calgary, Calgary, Alberta, Canada),
AC(University of Calgary, Calgary, Alberta, Canada),
AD(University of Calgary, Calgary, Alberta, Canada),
AE(National Oceanic and Atmospheric Administration,
Boulder, CO, US), AF(National Oceanic and
Atmospheric Administration, Boulder, CO, US),
AG(University of Oulu, Oulu, Finland), AH(University
of Oulu, Oulu, Finland), AI(Los Alamos National
Laboratory, Los Alamos, NM, US), AJ(Los Alamos
National Laboratory, Los Alamos, NM, US)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 100, no. A5, p. 7937-7969 (JGR Homepage)
Publication Date: 05/1995
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, EARTH MAGNETOSPHERE, GEOPHYSICS,
IONOSPHERIC STORMS, GEOMAGNETIC PULSATIONS,
GEOMAGNETISM, GEOSYNCHRONOUS ORBITS, MAGNETIC
STORMS, SOLAR WIND, STABILITY
Bibliographic Code: 1995JGR...100.7937E
Abstract
Multi-instrument data sets from the ground and satellites at both low
and high altitude have provided new results concerning substorm onset
and its source region in the magnetosphere. Twenty-six out of 37
substorm onset events showed evidence of azimuthally spaced auroral
forms (AAFs) prior to the explosive poleward motion associated with
optical substorm onset. AAFs can span 8 hours of local time prior to
onset and generally propagate eastward in the morning sector. Onset
itself is, however, more localized spanning only about 1 hour local
time. AAF onset occur during time periods when the solar wind pressure
is relatively high. AAFs brighten in conjunction with substorm onset
leading to the conclusion that they are a growth phase activity
casually related to substorm onset. Precursor activity associated with
these AAFs is also seen near geosynchronous orbit altitude and examples
show the relationship between the various instrumental definitions of
substorm onset. The implied mode number (30 to 135) derived from this
work is inconsistent with cavity mode resonances but is consistent with
a modified flute/ballooning instability which requires azimuthal
pressure gradients. The extended source region and the distance to the
open-closed field line region constrain reconnection theory and local
mechanisms for substorm onset. It is demonstrated that multiple onset
substorms can exist for which localized dipolarizations and the Pi 2
occur simultaneously with tail stretching existing elsewhere. These
pseudobreakups can be initiated by auroral streamers which originate at
the most poleward set of arc systems and drift to the more equatorward
main UV oval. Observations are presented of these AAFs in conjunction
with low- and high-altitutde particle and magnetic field data. These
place the activations at the interface between dipolar and taillike
field lines probably near the peak in the cross-tail current. These
onsets are put in the context of a new scenario for substorm morphology
which employs individual modules which operate independently or couple
together. This allows particular substorm events to be more accurately
described and investigated.
Title: Interpretation of optical substorm onset
observations
Authors: Murphree, J. S.; Elphinstone, R. D.; Henderson, M. G.;
Cogger, L. L.; Hearn, D. J.
Affiliation: AA(Calgary Univ., Canada), AB(Calgary Univ.,
Canada), AC(Calgary Univ., Canada), AD(Calgary
Univ., Canada), AE(Calgary Univ., Canada)
Journal: Journal of Atmospheric and Terrestrial Physics (ISSN
0021-9169), vol. 55, no. 8, p. 1159-1170.
Publication Date: 06/1993
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, EARTH MAGNETOSPHERE, GEOMAGNETIC TAIL,
MAGNETIC STORMS, VISUAL OBSERVATION, IONOSPHERIC
CURRENTS, MAGNETIC FIELD CONFIGURATIONS, SATELLITE
IMAGERY
Bibliographic Code: 1993JATP...55.1159M
Abstract
Several conclusions concerning the substorm onset region are made on
the basis of auroral observations taken by the UV Viking imager. In
particular, it is shown that the onset takes place in the poleward half
of the region of intense diffuse precipitation. The observations are
consistent with the conclusion that static magnetic field mapping
places the quiet time auroral oval source region within 20 earth radii
of the earth. It is also demonstrated that the large scale substorm
surge is likely to be contained well within the closed field line
region (with the possible exception of the eastwardmost arc system).
Title: Observations of distortions of optical features in
the UV auroral distribution
Authors: Murphree, John S.; Cogger, Leroy L.;
Elphinstone, R. D.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University, Canada)
Journal: IEEE Transactions on Plasma Science (ISSN
0093-3813), vol. 17, April 1989, p. 109-115.
Research supported by NSERC and Swedish Board for
Space Activities.
Publication Date: 04/1989
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, EARTH MAGNETOSPHERE, KELVIN-HELMHOLTZ
INSTABILITY, MAGNETIC VARIATIONS, SATELLITE
SOUNDING, VORTEX STREETS, CASSEGRAIN OPTICS, CHARGE
COUPLED DEVICES, NORTHERN HEMISPHERE,
SATELLITE-BORNE INSTRUMENTS
Bibliographic Code: 1989ITPS...17..109M
Abstract
Observations made by the Viking satellite have for the first time shown
the development of multiple large-scale surge features. The longer time
scale of these features is contrasted with smaller-scale vortex streets
found along the poleward edge of the evening oval, which are generally
observed to exist for less than 2 min. The ratio of wavelength to
diameter in these features is shown to decrease with increasing
wavelength. These observations support the view that the larger surge
features are the result of Kelvin-Helmholtz-type instabilities,
originating further out in the magnetosphere than their vortex-street
counterparts. Observations of spiral features have been made at all
local times, and the spirals always have a counterclockwise sense
(viewed in the direction of the magnetic field in the Northern
Hemisphere). One interpretation of these events is that they are the
result of an exponential growth along a field line of an initial upward
field-aligned-current perturbation.
Title: The double oval UV auroral distribution. 1:
Implications for the mapping of auroral arcs
Authors: Elphinstone, R. D.; Murphree, J. S.; Hearn, D. J.;
Cogger, L. L.; Sandahl, I.; Newell, P. T.; Klumpar, D. M.;
Ohtani, S.; Sauvaud, J. A.; Potemra, T. A.
Affiliation: AA(University of Calgary, Calgary, Canada),
AB(University of Calgary, Calgary, Canada),
AC(University of Calgary, Calgary, Canada),
AD(University of Calgary, Calgary, Canada),
AE(Swedish Institute for Space Physics, Kiruna,
Sweden), AF(Swedish Institute for Space Physics,
Kiruna, Sweden), AG(Lockheed Missiles and Space
Company Incorporated, Palo Alto, CA, US),
AH(Lockheed Missiles and Space Company Incorporated,
Palo Alto, CA, US), AI(Toulouse University,
Toulouse, France), AJ(Toulouse University, Toulouse,
France)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 100, no. A7, p. 12,075-12,092 (JGR Homepage)
Publication Date: 07/1995
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, DISTRIBUTION (PROPERTY), GEOPHYSICS,
LUMINOSITY, MAPPING, ULTRAVIOLET RADIATION, BOUNDARY
LAYER PLASMAS, EARTH IONOSPHERE, EARTH MAGNETOSPHERE
Bibliographic Code: 1995JGR...10012075E
Abstract
During the later stages of the auroral substorm the luminosity
distribution frequently resembles a double oval, one oval lying
poleward of the normal or main UV auroral oval. We interpret the double
oval morphology as being due to the plasma sheet boundary layer
becoming active in the later stages of the substorm process. If the
disturbance engulfs the nightside low-latitude boundary layers, then
the double oval configuration extends into the dayside ionospheric
region. The main UV oval is associated with the inner portion of the
central plasma sheet and can rapidly change its auroral character from
being diffuse to discrete. This transition is associated with the
substorm process and is fundamental to understanding the near-Earth
character of substorm onset. On the other hand, the poleward arc system
in the nightside ionosphere occurs adjacent to or near the open-closed
field line boundary. This system activates at the end of the optical
expansion phase and is a part of the recovery phase configuration in
substorms where it occurs. These two source regions for nightside
discrete auroral arcs are important in resolving the controversy
concerning the mapping of arcs to the magnetosphere. The dayside
extension of this double oval configuration is also investigated and
shows particle signatures which differ considerably from those on the
nightside giving clues to the magnetospheric source regions of the
aurora in the two local time sectors. Near-Earth substorm onsets are
shown to be coupled to processes occurring much further tailward and
indicate the importance of understanding the temporal development of
features within the double oval. Using 'variance images,' a new
technqiue for the investigation of these dynamics is outlined.
Title: On the electrodynamical state of the auroral
ionosphere during northward interplanetary magnetic
field - A transpolar arc case study
Authors: Marklund, G. T.; Blomberg, L. G.; Murphree, J. S.;
Elphinstone, R. D.; Zanetti, L. J.
Affiliation: AA(Royal Institute of Technology, Stockholm,
Sweden), AB(Royal Institute of Technology,
Stockholm, Sweden), AC(Calgary, University, Canada),
AD(Calgary, University, Canada), AE(Johns Hopkins
University, Laurel, MD)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 96, June 1, 1991, p. 9567-9578. Research
supported by Swedish National Space Board and U.S.
Navy. (JGR Homepage)
Publication Date: 06/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, AURORAL ZONES, ELECTRODYNAMICS,
INTERPLANETARY MAGNETIC FIELDS, SOLAR TERRESTRIAL
INTERACTIONS, CONVECTION CELLS, CONVECTION CURRENTS,
IONOSPHERIC DRIFT, MAGNETIC FIELD CONFIGURATIONS,
MAGNETOMETERS, RADAR MEASUREMENT
Bibliographic Code: 1991JGR....96.9567M
Abstract
The ionospheric electrodynamical state has been reconstructed for a
transpolar arc event during northward interplanetary magnetic field
conditions. An extensive set of observations by Viking and other
satellites and by ground-based radars has been used to provide
realistic model input data or to verify the modeling results. The
resulting convection pattern is found to be consistent with the Viking
electric field and intimately linked to the prevalent auroral
distribution. It is characterized by a large evening cell, well
extended across noon and split up by two separated potential minima,
and a minor crescent-shaped morning cell. The convection signatures are
found to vary a lot along the transpolar arc depending on the relative
role of the arc-associated convection and the ambient convection. The
transpolar arc is generally embedded in antisunward convective flow
except near the connection points with the auroral oval, where sunward
flow exists in localized regions.
Title: Wave characteristics obtained from OH rotational
temperatures and 557.7 nm airglow intensities
Authors: Cogger, L. L.; Elphinstone, R. D.; Giers, D. H.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University, Canada)
Journal: (IAGA, Symposium on Coupling, Energetics, Dynamics
and Electrodynamics of Atmospheric Regions,
Vancouver, Canada, Aug. 1987) Journal of Atmospheric
and Terrestrial Physics (ISSN 0021-9169), vol. 50,
Oct.-Nov. 1988, p. 943-949. Research supported by
NSERC.
Publication Date: 11/1988
Category: Geophysics
Origin: STI
NASA/STI Keywords: AIRGLOW, GRAVITY WAVES, HYDROXYL EMISSION, MOLECULAR
ROTATION, OXYGEN ATOMS, EARTH SURFACE, ROCKY
MOUNTAINS (NORTH AMERICA), UPPER ATMOSPHERE
Bibliographic Code: 1988JATP...50..943C
Abstract
Variations of OH rotational temperature and 557.7-nm atomic O intensity
were measured from Calgary, Canada, from 1985 to 1987. Observations
from three nights are discussed in detail, showing a correlation
between the OH rotational temperature wave structure at 85 km and the
green line emission at 95 km. This suggests that wave activity linked
the two regions. At 85 km, high and low frequency wave structure was
observed, but at 95 km the high frequency component disappeared. From
temperature data from 16 nights of wave activity, horizontal
wavelengths from about 5 to 100 km are derived and vertical wavelengths
from 0.7 to 8 km are inferred. It is suggested that the dominant source
of gravity waves in the mesopause region near Calgary is a result of
prevailing westerly winds blosing over the Rocky Mountains to the
southeast. No waves were observed propagating towards the southeast,
suggesting the presence of a filtering mechanism.
Title: Short-term dynamics of the high-latitude auroral
distribution
Authors: Murphree, J. S.; Elphinstone, R. D.; Cogger, L. L.;
Wallis, D. D.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(National Research Council of Canada,
Ottawa)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 94, June 1, 1989, p. 6969-6974. Research
supported by NSERC. (JGR Homepage)
Publication Date: 06/1989
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, NORTHERN HEMISPHERE, POLAR REGIONS,
SATELLITE IMAGERY, ULTRAVIOLET PHOTOGRAPHY, VIKING
ORBITER SPACECRAFT, INTERPLANETARY MAGNETIC FIELDS,
LYMAN SPECTRA, MORPHOLOGY
Bibliographic Code: 1989JGR....94.6969M
Abstract
During two consecutive orbits of the Viking satellite on March 24,
1986, UV observations of the Northern Hemisphere auroral distribution
revealed rapid growth and decay of large-scale polar arcs. Evolution of
these features occurred from the nightside auroral distribution toward
the dayside. The connection on the dayside was short-lived (about 2
min) and the arc retreated at similar speeds to its development (about
5 km/s). Examples of arc occurrences during a half-hour time period
show that arcs can extend from the nightside to the dayside and
disappear, and another extended arc can appear at a widely separated
position. These types of dynamic polar features appear consistent with
the dynamic energization and precipitation of boundary layer electrons
at high latitudes.
Title: Dynamics of the lower thermosphere consistent with
satellite observations of 5577 A airglow. I - Method
of analysis. II Atomic oxygen, local turbulence, and
global circulation results
Authors: Murphree, J. S.; Elphinstone, R. D.; Cogger, L. L.
Affiliation: AA(Calgary, University, Calgary, Alberta, Canada),
AB(Calgary, University, Calgary, Alberta, Canada),
AC(Calgary, University, Calgary, Alberta, Canada)
Journal: Canadian Journal of Physics (ISSN 0008-4204), vol.
62, April 1984, p. 370-395. Sponsorship: Natural
Sciences and Engineering Research Council of Canada.
Publication Date: 04/1984
Category: Geophysics
Origin: STI
NASA/STI Keywords: AIRGLOW, ATMOSPHERIC COMPOSITION, ATMOSPHERIC
MODELS, OXYGEN ATOMS, ATMOSPHERIC DIFFUSION,
ATMOSPHERIC TURBULENCE, WIND EFFECTS
Bibliographic Code: 1984CaJPh..62..370M
Abstract
Not Available
Title: Simultaneous prenoon and postnoon observations of
three field-aligned current systems from Viking and
DMSP-F7
Authors: Ohtani, S.; Potemra, T. A.; Newell, P. T.; Zanetti, L. J.;
Iijima, T.; Watanabe, M.; Yamauchi, M.;
Elphinstone, R. D.; de La Beauijardie, O.;
Blomberg, L. G.
Affiliation: AA(Johns Hopkins Univ., Laurel, MD, US), AB(Johns
Hopkins Univ., Laurel, MD, US), AC(Johns Hopkins
Univ., Laurel, MD, US), AD(Johns Hopkins Univ.,
Laurel, MD, US), AE(Univ, of Tokyo, Tokyo, Japan),
AF(Univ, of Tokyo, Tokyo, Japan), AG(Swedish
Institute of Space Physics, Kiruba, Sweden),
AH(Swedish Institute of Space Physics, Kiruba,
Sweden), AI(SRI International, Menlo Park, CA, US),
AJ(SRI International, Menlo Park, CA, US)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 100, no. A1, p. 119-136 (JGR Homepage)
Publication Date: 01/1995
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, EARTH IONOSPHERE, EARTH MAGNETOSPHERE,
FIELD ALIGNED CURRENTS, INTERPLANETARY MAGNETIC
FIELDS, PARTICLE PRECIPITATION, SPATIAL
DISTRIBUTION, CONVECTIVE FLOW, DAYTIME, DMSP
SATELLITES, GRAPHS (CHARTS), TABLES (DATA), VIKING
SPACECRAFT
Bibliographic Code: 1995JGR...100..119O
Abstract
The spatial structure of dayside large-scale field-aligned current
(FAC) systems is examined by using Viking and Defense Meteorological
Satellite Program-F7 (DMSP-F7) data. We focus on four events in which
the satellites simultaneously observed postnoon and prenoon three FAC
systems: the region 2, the region 1, and the mantle (referred to as
midday region O) systems, from equatorward to poleward. These events
provide the most solid evidence to date that the midday region O system
is a separate and unique FAC system, and is not an extension of the
region 1 system from other local times. The events are examined
comprehensively by making use of a mulit-instrumental data set, which
includes magnetic field, particle flux, electric field, auroral UV
image data from the satellites, and the Sondrestrom convection data.
The results are summarized as follows: (1) Region 2 currents flow
mostly in the central plasma sheet (CPS) precipitation region, often
overlapping with the boundary plasma sheet (BPD) at their poleward
edge. (2) The region 1 system is located in the core part of the
auroral oval and is confined in a relatively narrow range in latitude
which includes the convection reversal. The low-latitude boundary
layer, possibly including the outer part of the plasma sheet, and the
external cusp are the major source regions of dayside region 1
currents. (2) Midday region O currents flow on open field lines and are
collocated with the shear of antisunward convection flows with
velocites decreasing poleward. On the basis of these results we support
the view that both prenoon and postnoon current systems consist of the
three-sheet structure when the disctortion ofthe convection pattern
associated with interplanetary magnetic field (IMF) B(sub Y) is small
and both morningside and eveningside convection cells are
crescent-shaped. We also propose that the midday region O and a part of
the region 1 systems are closely coupled to the same source.
Title: The double oval UV auroral distribution. 2: The most
poleward arc system and the dynamics of the
magnetotail
Authors: Elphinstone, R. D.; Hearn, D. J.; Cogger, L. L.;
Murphree, J. S.; Wright, A.; Sandahl, I.; Ohtani, S.;
Newell, P. T.; Klumpar, D. M.; Shapshak, M.
Affiliation: AA(University of Calgary, Calgary, Canada),
AB(University of Calgary, Calgary, Canada),
AC(University of Calgary, Calgary, Canada),
AD(University of Calgary, Calgary, Canada),
AE(University of St. Andrews, St. Andrews, Fife,
UK), AF(University of St. Andrews, St. Andrews,
Fife, UK), AG(Johns Hopkins University, Laurel, MD,
US), AH(Johns Hopkins University, Laurel, MD, US),
AI(Lockheed Missiles and Space Company Incorporated,
Palo Alto, CA, US), AJ(Lockheed Missiles and Space
Company Incorporated, Palo Alto, CA, US)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 100, no. A7, p. 12,093-12,102 (JGR Homepage)
Publication Date: 07/1995
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, GEOMAGNETIC TAIL, GEOPHYSICS,
ULTRAVIOLET RADIATION, ATMOSPHERIC BOUNDARY LAYER,
BOUNDARY LAYER PLASMAS, DISTRIBUTION (PROPERTY),
LUMINOSITY
Bibliographic Code: 1995JGR...10012093E
Abstract
The poleward arc system of a double oval distribution is shown to
activate at the end of the optical expansion phase signifying the
beginning of substorm recovery. The velocity dispersed ion signature
(VDIS) can exist coincident with this discrete aurora developing on the
most poleward oval. Although the VDIS is usually associated with ion
beams in the plasma sheet boundary layer, it is demonstrated that the
ionospheric signature is not beamlike but distributed in pitch angle.
At the time when the double oval begins to form, the magnetic field in
the magnetotail lobe becomes less flared and can show Pc 5 period
oscillations. Similar pulsations also exist in the ionosphere
associated with the most poleward oval and with stationary surge
formation. Theoretical considerations link this phenomenon with a wave
source tailward of x(sub GSE) = -30R(sub E) and fast mode evanescent
waves propagating earthward in the tail lobe region. In this case the
magnetotail appears to act like a waveguide and the plasma sheet
boundary layer as a resonance region. This implies that the coupling of
this fast mode waves is with the plasma sheet boundary layer and not
with dipolar like field lines. The implications of this for the
reconnection model of substorms are discussed.
Title: Four large-scale field-aligned current systmes in
the dayside high-latitude region
Authors: Ohtani, S.; Potemra, T. A.; Newell, P. T.; Zanetti, L. J.;
Iijima, T.; Watanabe, M.; Blomberg, L. G.;
Elphinstone, R. D.; Murphree, J. S.; Yamauchi, M.
Affiliation: AA(Johns Hopkins Univ., Laurel, MD, US), AB(Johns
Hopkins Univ., Laurel, MD, US), AC(Johns Hopkins
Univ., Laurel, MD, US), AD(Johns Hopkins Univ.,
Laurel, MD, US), AE(Univ. of Tokyo, Tokyo, Japan),
AF(Univ. of Tokyo, Tokyo, Japan), AG(Royal Institute
of of Technology, Stockholm, Sweden), AH(Royal
Institute of of Technology, Stockholm, Sweden),
AI(Univ. of Calgary, Calgary, Alberta, Canada),
AJ(Univ. of Calgary, Calgary, Alberta, Canada)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 100, no. A1, p. 137-153 (JGR Homepage)
Publication Date: 01/1995
Category: Geophysics
Origin: STI
NASA/STI Keywords: CURRENT SHEETS, DAYTIME, EARTH IONOSPHERE, ELECTRON
PRECIPITATION, FIELD ALIGNED CURRENTS, HIGH ENERGY
ELECTRONS, POLAR REGIONS, CONVECTIVE FLOW,
CORRELATION, DMSP SATELLITES, ELECTRIC FIELDS,
INTERPLANETARY MAGNETIC FIELDS, VIKING SPACECRAFT
Bibliographic Code: 1995JGR...100..137O
Abstract
A system of four current sheets of large-scale field-aligned currents
(FACs) was discovered in the data set of simultaneous Viking and
Defense Meteorological Satellire Program-F7 (DMSP-F7) crossing of the
dayside high-latitude region. This paper reports four examples of this
system that were observed in the prenoon sector. The flow polarities of
FACs are upward, downward, upward, and downward, from equatorward to
poleward. The lowest-latitude upward current is flowing mostly in the
central plasma sheet (CPS) precipitation region, often overlapping with
the boundary plasma sheet (BPS) at its poleward edge, andis interpreted
as a region 2 current. The pair of downward and upward FACs in the
middle of te structure are collocated with structured electron
precipitation. The precipitation of high-energy (greater than 1 keV)
electrons is more intense in the lower-latitude downward current sheet.
The highest-latitude downward flowing current sheet is located in a
weak, low-energy particle precipitation region, suggesting that this
current is flowing on open field lines. Simulaneous observations in the
postnoon local time sector reveal the standard three-sheet structure of
FACs, sometimes described as region 2, region 1, and mantle (referred
to the midday region O) currents. A high correlation was found between
the occurrence of the four FAC sheet structure and negative
interplanetary magnetic field (IMF) B(sub Y). We discuss the FAC
structurein terms of three types of convection cells: the merging,
viscous, andlobe cells. During strongly negative IMF B(sub Y), two
convection reversals exist in the prenoon sector; one is inside the
viscous cell, and the other is between the viscous cell and the lobe
cell. This structure of convection flow is supported by the Viking
electric field and auroral UV image data. Based on the convection
pattern, the four FAC sheet structure is interpreted as the latitude
overlap of midday and morning FAC systems. We suggest that the
for-current sheet structure is common in a certain prenoon localtime
sector during strongly negative IMF B(sub Y).
Title: A new type of ion injection event observed by Viking
Authors: Yamauchi, M.; Woch, J.; Lundin, R.; Shapshak, M.;
Elphinstone, R.
Affiliation: AA(Swedish Inst. of Space Physics, Kiruna, Sweden),
AB(Max-Planck-Inst. fuer Aeronomie,
Katlenburg-Lindau, Germany), AC(Swedish Inst. of
Space Physics, Kiruna, Sweden), AD(Royal Inst. of
Technology, Stockholm, Sweden), AE(Calgary Univ.,
Canada)
Journal: Geophysical Research Letters (ISSN 0094-8276), vol.
20, no. 9, p. 795-798. (GeoRL Homepage)
Publication Date: 05/1993
Category: Geophysics
Origin: STI
NASA/STI Keywords: ION INJECTION, SOLAR TERRESTRIAL INTERACTIONS, SOLAR
WIND, SPACE PLASMAS, VIKING SPACECRAFT, ELECTRIC
FIELDS, GEOMAGNETISM, MAGNETOSHEATH
Bibliographic Code: 1993GeoRL..20..795Y
Abstract
The discovery of a new type of low-energy (less than 200 eV) plasma
injection event near local noon several degrees equatorward of the cusp
is reported. Its V-shaped energy-pitch angle pattern is very similar to
that of impulsive or transient magnetosheath plasma injection events
reported in the past. Thus, the source region of these injected
particles is not a persistent one and it is likely of magnetosheath
origin. The magnetic field and the electric field observations do not
exhibit a strong electromagnetic coupling between the ionosphere and
the source region. A high-energy (greater than 300 eV) population is
absent, making the ion energy-time dispersion very weak. This event
does not seem to be related to either any solar wind density increase
or southward/disturbed interplanetary magnetic field conditions. It is
suggested that this is a more stagnant phenomenon.
Title: Geographic asymmetries of the Viking auroral
distribution - Implications for ionospheric
coordinate systems
Authors: Hearn, D. J.; Elphinstone, R. D.; Murphree, J. S.;
Cogger, L. L.
Affiliation: AA(Calgary Univ., Canada), AB(Calgary Univ.,
Canada), AC(Calgary Univ., Canada), AD(Calgary
Univ., Canada)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 98, no. A2, p. 1653-1667. (JGR Homepage)
Publication Date: 02/1993
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, SATELLITE IMAGERY, EARTH IONOSPHERE,
GEOMAGNETIC TAIL
Bibliographic Code: 1993JGR....98.1653H
Abstract
A number of old concepts concerning the Viking auroral distribution are
reexamined on the basis of the current understanding of the
magnetosphere. Two new coordinate systems are described using
magnetospheric magnetic field models which leave the aurora invariant
under a much wider range of conditions than was previously possible.
The cross-tail current running from dawn to dusk in the near-earth
magnetotail maps to a circular distribution if a centered dipole field
is used in combination with the external field. The diameter of the
main UV auroral oval can be linked directly to the strength and
location of the peak in the cross-tail current distribution. Model
calculations and observations indicate that the auroral distribution
can have significant deviations from circularity even in corrected
geomagnetic coordinates. The auroral distribution moves equatorward
with increasing magnetic activity in response to an enhanced cross-tail
current which moves eastward.
Title: Viking observations of the UV dayside aurora and
their relationship to DMSP particle boundary
definitions
Authors: Elphinstone, R. D.; Murphree, J. S.; Hearn, D. J.;
Cogger, L. L.; Newell, P. T.; Vo, H.
Affiliation: AA(Calgary Univ., Canada), AB(Calgary Univ.,
Canada), AC(Calgary Univ., Canada), AD(Calgary
Univ., Canada), AE(Johns Hopkins Univ., Laurel, MD),
AF(Calgary Univ., Canada)
Journal: Annales Geophysicae (ISSN 0992-7689), vol. 10, no.
11-12, p. 815-826. (AnGeo Homepage)
Publication Date: 12/1992
Category: Geophysics
Origin: STI
NASA/STI Keywords: ATMOSPHERIC PHYSICS, AURORAS, POLAR CUSPS,
ULTRAVIOLET EMISSION, DAYTIME, DMSP SATELLITES,
PARTICLE PRECIPITATION
Bibliographic Code: 1992AnGeo..10..815E
Abstract
Satellite optical observations and particle measurements are combined
here to provide an intercalibration between Viking UV observations of
the dayside aurora and DMSP-F7 particle boundary definitions. The main
auroral distribution is usually continuous through the noon sector
between 8 and 16 MLT. There is generally good correspondence between
the Viking UV aurora and the DMSP particle signatures. The mantle and
cusp particle signatures from DMSP usually result in little if any
Viking UV response and consistently appear poleward of the main auroral
distribution. Magnetic field mapping indices that in addition to the
observed DMSP particle cusps there may be a special cusp signature more
closely related to magnetospheric topology. There sometimes appears to
be a boundary between the mantle and polar rain particle signatures
which is associated with a high-latitude auroral feature, poleward and
parallel to the auroral 'oval'.
Title: Oval intensification event observed by STARE and
Viking
Authors: Nielsen, E.; Elphinstone, R.; Hearn, D.; Murphree, J. S.;
Potemra, T.
Affiliation: AA(Max-Planck-Inst. fuer Aeronomie,
Katlenburg-Lindau, Germany), AB(Calgary Univ.,
Canada), AC(Calgary Univ., Canada), AD(Calgary
Univ., Canada), AE(Johns Hopkins Univ., Laurel, MD)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 98, no. A4, p. 6163-6171. (JGR Homepage)
Publication Date: 04/1993
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, AURORAL ELECTROJETS, EARTH IONOSPHERE,
MAGNETIC STORMS, ULTRAVIOLET PHOTOGRAPHY, VIKING
ORBITER SPACECRAFT, EARTH MAGNETOSPHERE, RADAR
TRACKING, SATELLITE-BORNE INSTRUMENTS
Bibliographic Code: 1993JGR....98.6163N
Abstract
Optical emissions and electron flow patterns in the auroral oval
evening sector have been investigated in the 30-min interval prior to a
major auroral intensification. The STARE radar and Viking UV image data
were combined to give a dynamical picture of the auroral ionosphere
just to the west of the intensification region which was bordered on
its eastward side by the foot of a high-latitude polar arc. Half an
hour prior to the main intensification an auroral arc appeared
equatorward of a band of eastward electrojet, which in turn was
equatorward of another discrete arc system. The appearance of the new
arc system was accompanied by a second eastward electrojet further
equatorward. Within minutes of this appearance the older electrojet and
arc system faded and the new system moved poleward to replace it. This
precursor activity was followed by a major intensification, a substorm,
to the east of the foot of the high-latitude polar arc. It is
speculated that the precursor is linked to changes in the current
distribution in the near-Earth nightside magnetosphere prior to the
substorm onset.
Title: Satellite observations of polar arcs
Authors: Murphree, J. S.; Austin, J. B.; Hearn, D. J.; Cogger, L. L.;
Elphinstone, R. D.; Woch, J.
Affiliation: AA(Univ. of Calgary, Calgary, Alberta, Canada),
AB(Univ. of Calgary, Calgary, Alberta, Canada),
AC(Univ. of Calgary, Calgary, Alberta, Canada),
AD(Univ. of Calgary, Calgary, Alberta, Canada),
AE(Univ. of Calgary, Calgary, Alberta, Canada),
AF(Univ. of Calgary, Calgary, Alberta, Canada)
Journal: Journal of Atmospheric and Terrestrial Physics (ISSN
0021-9169), vol. 56, no. 2, p. 265-284
Publication Date: 02/1994
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, INTERPLANETARY MAGNETIC FIELDS,
MAGNETIC FIELD CONFIGURATIONS, MAGNETOHYDRODYNAMIC
FLOW, POLAR REGIONS, RADIO EMISSION, SATELLITE
OBSERVATION, ELECTRODYNAMICS, GEOMAGNETISM, MAGNETIC
SIGNATURES, MAGNETIC STORMS,
MAGNETOSPHERE-IONOSPHERE COUPLING, MAGNETOSPHERES,
POLAR CUSPS, TOPOLOGY
Bibliographic Code: 1994JATP...56..265M
Abstract
The increased probability of observing polar arcs during periods of
northward interplanetary magnetic field (IMF) has tended to obscure
their significance in terms of magnetospheric topology because of the
presumed 'inactive' state of the magnetosphere. However, satellite
imaging has shown that these high latitude features are quite dynamic
both in their intensity and spatial variations. The overall morphology
of the high latitude aurora has been described by a variety of
imaginative terms, but its primary optical characteristic is of a polar
arc(s) extending between the dayside and nightside auroral distribution
on one or both of the dawn/dusk sides of the high latitude region. This
large scale morphology is controlled by the azimuth angle of the IMF
and the predominant configuration is one wherein the region between the
polar arc and the normal auroral distribution is filled with low
intensity diffuse emission. Simultaneous particle and electric field
measurements show this region exhibits a closed field line character
with predominantly sunward flowing plasma. These large scale polar arcs
are connected (in either a diffuse or discrete fashion) to the
nightside auroral distribution with essentially equal probabilities,
but exhibit a clear peak near 12 MLT. This dayside connection is
commonly associated with isolated high latitude features poleward of
the normal auroral distribution which probably represent processes
occurring on the front surface of the magnetotail poleward of the cusp.
The existence of polar arcs is not always controlled by substorm
activity: polar arcs can maintain their form and position well past
expansion phase suggesting that they represent a fundamental boundary
in the magnetosphere which is not modified by even large substorms.
Title: The analysis of hydroxyl rotational temperatures to
characterize moving thermal structures near the
mesopause
Authors: Elphinstone, R. D.; Cogger, L. L.; Murphree, J. S.;
Murty, G. S. N.; Meriwether, J. W., Jr.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(Calgary, University, Canada),
AE(Michigan, University, Ann Arbor)
Journal: Journal of Atmospheric and Terrestrial Physics (ISSN
0021-9169), vol. 50, July 1988, p. 657-669.
NSERC-NSF-supported research.
Publication Date: 07/1988
Category: Geophysics
Origin: STI
NASA/STI Keywords: ATMOSPHERIC CIRCULATION, HYDROXYL RADICALS,
MESOPAUSE, MOLECULAR ROTATION, TEMPERATURE
DISTRIBUTION, CLOUD PHYSICS, FRONTS (METEOROLOGY),
MERIDIONAL FLOW
Bibliographic Code: 1988JATP...50..657E
Abstract
Hydroxyl rotational temperatures near 85 km altitude have been measured
at Calgary, Canada in order to determine velocities, wavelengths, and
periods associated with moving temperature structures. The velocity of
moving patterns in two-dimensional data sets is used as a parameter for
a global smoothing algorithm. It is found that velocities of the
structures in the meridional direction were directed poleward, and that
the corresponding Doppler bulk wind velocities measured near the 95 km
height region were directed equatorward, suggesting the presence of
filtering of internal gravity waves by the background wind. Two
coherent wave structures were often detected simultaneously during a
night.
Title: Field line resonance interference model for multiple
auroral are generation
Authors: Lyatsky, W.; Elphinstone, R. D.; Pao, Q.;
Cogger, L. L.
Journal: Journal of Geophysical Research, Volume 104, Issue
A1, p. 263-268 (JGR Homepage)
Publication Date: 01/1999
Origin: AGU
AGU Keywords: Magnetospheric Physics: Auroral phenomena,
Ionosphere: Auroral ionosphere
Abstract Copyright: (c) 1999: American Geophysical Union
DOI: 10.1029/1998JA900027
Bibliographic Code: 1999JGR...104..263L
Abstract
A simple model for the generation of poleward moving multiple auroral
structures in the nightside ionosphere is described. The model is based
upon the premise that field line resonance oscillations are responsible
for auroral arc generation. The auroral structures are considered to be
a result of interference between Alfven field line resonance
oscillations on different L shells. Because of the dependence of the
Alfven resonance frequency on L shell, any two neighboring L shells
which oscillated initially with the same phase, after some time appear
to be in opposite phase. That results in the appearance of
counter-directed electric fields at these L shells and a large
field-aligned current between them, which can produce the electron
acceleration along the magnetic field and be responsible for auroral
arc generation. The out of phasing between the oscillating L shells
begins first at low latitudes and then propagates poleward producing
poleward moving auroral arcs. The model requires that oscillations be
maintained for many cycles of the waves and the source for energy is
ultimately derived from magnetospheric convection in the plasma sheet.
The field line resonance interference model explains periodic behavior
in such auroral activity having frequencies in the Pc5 range. It is
significant that the period of oscillation may be greater than that for
the Alfven resonant oscillations, which implies that two separate
frequencies may appear on the same field line. The poleward propagation
of the auroral arcs in this model is a result of the poleward
propagation of interference maxima rather than any real plasma or wave
propagation.
Title: Comparison of UV optical signatures with the
substorm current wedge as predicted by an inversion
algorithm
Authors: Sergeev, V. A.; Vagina, L. I.; Elphinstone, R. D.;
Murphree, J. S.; Hearn, D. J.; Cogger, L. L.;
Johnson, M. L.
Journal: Journal of Geophysical Research, Volume 101, Issue
A2, p. 2615-2628 (JGR Homepage)
Publication Date: 02/1996
Origin: AGU
AGU Keywords: Ionosphere: Auroral ionosphere, Magnetospheric
Physics: Auroral phenomena, Ionosphere: Current
systems, Magnetospheric Physics: Storms and
substorms
DOI: 10.1029/95JA00537
Bibliographic Code: 1996JGR...101.2615S
Abstract
Optical images of the auroral bulge as seen by the Viking UV imager
were compared in several cases with the substorm current wedge (SCW)
upward and downward field-aligned currents (FAC) whose positions were
determined using the inversion algorithm based on the substorm-related
magnetic variations observed at midlatitudes. With reasonable accuracy
(better than 0.5 hours MLT) the estimated longitudes of the upward FAC
generally pointed to the surge or to the brightest luminousity region
in the western half of the bulge. The latter feature may imply a more
complicated structure of the net FACs than can be described by the
simple substorm current wedge scheme. Similarly, the estimated
positions of the downward FAC pointed close to the eastern termination
of the bulge. The associated optical signatures of this current system
ranged from the well-defined emission depletion regions to new auroral
intensifications. The downward current appears to correspond in some
cases at least with the division between the morning sector portion of
the double oval and the nightside portion connected more directly to
the substorm bulge. The results in general confirm the expected
association between the auroral bulge and the SCW, as well as showing a
reasonably good results from the inversion algorithm based on
midlatitude magnetic observations. Our results, however, also indicate
that one must be careful in interpreting the apparent motion of
SCW-related field-aligned currents inferred from midlatitude
observations in terms of a true westward or eastward expansion of the
SCW or of the auroral bulge. The observed changes may instead sometimes
be related to the redistribution of the net FACs within than a shift or
expansion of the simple current system.
Title: A technique for the analysis of two-dimensional data
Application to OI 5577 A airglow
Authors: Elphinstone, R.; Murphree, J. S.; Cogger, L. L.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University, Canada)
Journal: Journal of Atmospheric and Terrestrial Physics (ISSN
0021-9169), vol. 48, March 1986, p. 213-220.
Publication Date: 03/1986
Category: Geophysics
Origin: STI
NASA/STI Keywords: AIRGLOW, DATA PROCESSING, E REGION, OXYGEN IONS,
SATELLITE OBSERVATION, ANNUAL VARIATIONS, DATA
BASES, EMISSION SPECTRA, FUNCTIONS (MATHEMATICS),
GEOMAGNETIC LATITUDE, ISIS-B, SIGNAL TO NOISE
RATIOS, TEMPORAL DISTRIBUTION
Bibliographic Code: 1986JATP...48..213E
Abstract
A method to determine whether a two-dimensional data set can be
represented by two independent separable functions is demonstrated
using both synthetic data and satellite observations of OI 5577 A
airglow. For such cases when the functions are separable it is possible
to identify the function in the presence of noise using an iterative
procedure based on the properties of an equitable matrix. In the
specific case of the airglow, the latitudinal and temporal variations
are separable for the data set studied. The spatial structure shows a
minimum near the equator, with maxima at 35 deg in the winter
hemisphere and 25 deg in the summer hemisphere. The long-term temporal
function shows maxima after the equinoxes, with minima near the
solstice. A 12 month component has a maximum near day 300.
Title: Phase mixing and phase motion of Alfv? waves on
tail-like and dipole-like magnetic field lines
Authors: Wright, Andrew N.; Allan, W.; Elphinstone, R. D.;
Cogger, L. L.
Journal: Journal of Geophysical Research, Volume 104, Issue
A5, p. 10159-10176 (JGR Homepage)
Publication Date: 05/1999
Origin: AGU
AGU Keywords: Magnetospheric Physics: MHD waves and instabilities,
Space Plasma Physics: Kinetic and MHD theory,
Ionosphere: Auroral ionosphere, Magnetospheric
Physics: Magnetotail
Abstract Copyright: (c) 1999: American Geophysical Union
DOI: 10.1029/1999JA900018
Bibliographic Code: 1999JGR...10410159W
Abstract
The time-dependent phase structure of Alfv? waves on open and closed
field lines is studied. In accord with previous observations we find
that Alfv? waves on near-Earth closed field lines exhibit a poleward
phase motion unless they are close to the plasmapause, in which case
the motion may be equatorward. Alfv? waves generated on tail-like
closed or open field lines threading the plasma sheet boundary layer
have received much less attention but may be shown to have an
equatorward phase motion [Liu et al., 1995]. Phase mixing in the
magnetotail proves to have a much richer behavior than that of
near-Earth (dipole-like) closed field lines as not only the Alfv?
frequency varies across the background field lines but the
field-aligned wavenumber varies too. The two contributions tend to
cancel each other partially for typical tail equilibria. Observations
are given of a double oval configuration showing long-period pulsations
on the poleward portion of this oval. Equatorward phase motion is
observed and supports the theory presented here. These observations
illustrate that Pc5 pulsation activity can be much richer than
previously thought and can occur at locations not in the dipole-like
region, as is usually supposed. The concepts presented in this paper
provide a powerful framework with which to interpret observations
related to auroral arcs, substorms, and magnetospheric equilibria.
Title: The response of the quiet-time auroral configuration
to short- and long-term interplanetary magnetic
field variations
Authors: Murphree, J. S.; Cogger, L. L.; Elphinstone, R. D.;
Hearn, D.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(Calgary, University, Canada)
Journal: Canadian Journal of Physics (ISSN 0008-4204), vol.
69, Aug.-Sept. 1991, p. 1040-1046. Research
supported by NSERC.
Publication Date: 09/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ZONES, INTERPLANETARY MAGNETIC FIELDS, SOLAR
ACTIVITY, IMP, SOLAR TERRESTRIAL INTERACTIONS,
VIKING SPACECRAFT
Bibliographic Code: 1991CaJPh..69.1040M
Abstract
Observations from the IMP-8 satellite of the IMF are compared with
areas of the polar region bounded by the aurora as observed by the
Viking spacecraft during quiet-time conditions (IMF Bz northward). A
variety of energy-coupling functions are investigated and it is
determined that the auroral distribution can be best described by the
inclusion of azimuthal terms in addition to standard energy-coupling
functions. The auroral distributions for Bz northward support
antiparallel merging as a mechanism whereby energy is transferred to
the magnetosphere from the solar wind. When the polar angle is small
the region bounded by the auroras expands and may be controlled more by
wave interaction at the magnetopause. Observations by the Viking
spacecraft indicate a dominance of dusk sector polar arcs in the spring
time and dawn sector arcs in the fall. Two alternative mechanisms can
explain the observations. One involves the ordering of the IMF in a
solar equatorial coordinate system while the other involves the sun's
polarity and the traversal of the earth's orbit through different
heliographic latitudes. A test is proposed whereby the two hypotheses
can be investigated during the next solar cycle.
Title: Auroral kilometric radiation from transpolar arcs
Authors: Pedersen, B. M.; Pottelette, R.; Eliasson, L.;
Murphree, J. S.; Elphinstone, R. D.; Bahnsen, A.;
Jespersen, M.
Affiliation: AA(Paris, Observatoire, Meudon, France), AB(Centre
de Recherches en Physique de l'Environnement
Terrestre et Planetaire, Saint-Maur-des-Fosses,
France), AC(Swedish Institute of Space Physics,
Kiruna, Sweden), AD(Calgary, University, Canada),
AE(Calgary, University, Canada), AF(Danish Space
Research Institute, Lyngby, Denmark), AG(Danish
Space Research Institute, Lyngby, Denmark)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 97, no. A7, July 1, 1992, p. 10,567-10,573.
Research supported by CNES and INSU. (JGR Homepage)
Publication Date: 07/1992
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, ION BEAMS, KILOMETRIC WAVES,
ULTRAVIOLET SPECTRA, VIKING SPACECRAFT, AURORAL
ZONES, COLD PLASMAS, ELECTROSTATIC WAVES, HIGH
FREQUENCIES
Bibliographic Code: 1992JGR....9710567P
Abstract
The relationship between auroral kilometric radiation (AKR) and
discrete auroral features is studied with satellite observations. AKR
generation is most often associated with nightside aurora, but under
certain circumstances the source regions may also occur on discrete
features identified as transpolar arcs. The wave spectrograms detected
during crossings or closest approaches to such sources exhibit
structures similar to those observed during nightside AKR source
crossings. Also, the associated ion beams and trapped conical electron
populations with enhanced upward directed loss cones peak at comparable
energies.
Title: Special features of a substorm during high solar
wind dynamic pressure
Authors: Lui, A. T. Y.; Elphinstone, R. D.; Murphree, J. S.;
Henderson, M. G.; Vo, H. B.; Cogger, L. L.; L?r, H.;
Ohtani, S.; Newell, P. T.; Reeves, G. D.
Journal: Journal of Geophysical Research, Volume 100, Issue
A10, p. 19095-19108 (JGR Homepage)
Publication Date: 10/1995
Origin: AGU
AGU Keywords: Ionosphere: Auroral ionosphere, Magnetospheric
Physics: Auroral phenomena, Magnetospheric Physics:
Storms and substorms, Magnetospheric Physics:
Magnetospheric configuration and dynamics
DOI: 10.1029/95JA01181
Bibliographic Code: 1995JGR...10019095L
Abstract
A substorm on July 24, 1986, exhibiting a rather unusual auroral
morphology is analyzed with data from 10 spacecraft (Viking; DMSP F6
and F7; GOES 5 and 6; three LANL geosynchronous satellites; CCE; and
IMP 8). This substorm occurred during high solar wind dynamic pressure
(>5 nPa). Several notable features for this substorm are (1) the
substorm onset activity was preceded by prominent auroral activations
in the morning sector with spatial separations between adjacent bright
regions ranging from ~160 to 640 km, and their intensity was modulated
at ~3.2-min intervals; (2) the initial substorm activity was
concentrated in the morning sector, followed by a sudden activation in
the dusk sector, leaving the midnight sector relatively undisturbed, in
sharp contrast to the traditional substorm development in which the
major activity occurs in the midnight sector; (3) while a substorm
injection was observed at a geocentric distance of ~8.4 RE
by CCE in association with the substorm onset, particle injections
(detectable with three LANL geosynchronous satellites) and
dipolarization signatures (detectable by the two GOES satellites) were
not observed until subsequent intensifications; (4) timing subsequent
substorm intensifications from injections at the geosynchronous
altitude differed from timing intensifications based on Viking auroral
images by as much as ~3 min even when the auroral activity occurred in
the same magnetic local time sector as the geosynchronous satellite;
(5) the polar cap boundary was at a significantly higher latitude than
the poleward boundary delineated by detectable auroral luminosity in
the auroral oval, supporting the previous result that auroral activity
at substorm onset occurs substantially equatorward of the boundary
between open and closed magnetic field lines.<p>Detailed timing
analysis suggests the substorm onset to be associated with southward
interplanetary magnetic field (IMF), with the crossing of an IMF sector
boundary (interplanetary current sheet). The dimming of auroral
luminosity in the midnight region was associated with a sudden
northward turning of the IMF during high solar wind dynamic pressure
condition. .
Title: Multipoint observations of a dayside transient event
Authors: Vo, H. B.; Murphree, J. S.; Elphinstone, R. D.;
Elphic, R. C.; Friis-Christensen, E.; Luhr, H.;
Sibeck, D. G.
Affiliation: AA(University of Calgary, Calgary, Alberta, Canada),
AB(University of Calgary, Calgary, Alberta, Canada),
AC(University of Calgary, Calgary, Alberta, Canada),
AD(University of Calgary, Calgary, Alberta, Canada),
AE(Danish Meteorological Institute, Copenhagen,
Denmark), AF(Danish Meteorological Institute,
Copenhagen, Denmark), AG(Johns Hopkins University,
Laurel, MD, US)
Journal: Journal of Geophysical Research (ISSN 0148-0227),
vol. 99, no. A7, p. 13,409-13,423 (JGR Homepage)
Publication Date: 01/1994
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, FIELD ALIGNED CURRENTS, GEOMAGNETIC
PULSATIONS, GEOSYNCHRONOUS ORBITS, INTERPLANETARY
MAGNETIC FIELDS, MAGNETIC FIELD RECONNECTION,
MAGNETOPAUSE, VORTICES, EXPLORER 50 SATELLITE,
INTERNATIONAL SUN EARTH EXPLORERS,
MAGNETOSPHERE-IONOSPHERE COUPLING, SOLAR TERRESTRIAL
INTERACTIONS, SOLAR WIND
Bibliographic Code: 1994JGR....9913409V
Abstract
Many different processes may take place at the magnetopause. To
distinguish the various mechanisms requires simultaneous multipoint
observations in the dayside magnetosphere. Such coincident observations
were made by a number of spacecraft located in the solar wind, at the
magnetopause, at geosynchronous orbit, and at polar orbit on September
23, 1986. Beginning at 1110 UT, the B(sub z) component of the
Interplanetary Magnetic Field (IMF) underwent three periodic cycles,
each with a duration of about 7 min, and there were 4 solar wind
pressure pulses with a period of 10 min, as recorded by the
Interplanetary Monitroing Platform (IMP) 8 satellite. The International
Sun Earth Explorer (ISEE) satellite pair crossed the magnetopause near
local noon at 1125 UT and recorded two bipolar events in the normal
component of the magnetic field at 1115 and 1120 UT. In addition, ISEE
1 observed a bipolar event at 1118 UT that ISEE 2 did not. Periodic
oscillations and compressions of the magnetic field were then
subsequently seen at geosynchronous orbit in the dawn sector. Greenland
magnetometer stations also located in the morning sector recorded
transient responses to the solar wind pressure pulses. The East Coast
stations (near local noon) apparently observed a different vortex at
1122 UT. Viking auroral images show an activation of a localized
feature poleward of the dayside auroral distribution at 1122 UT. An
auroral enhancement, seen at 1128 UT in the afternoon sector, moved
eastward at a speed of 5 km/sec and decayed in intensity by 1141 UT.
Clear Pc 5 pulsations were seen equatorward of this activation.
Differences in both in situ measurements and ionospheric responses to
the two bipolar events lead to the conclusion that the 1118 UT event
can be interpreted as being associated with reconnection at the same
time that the magnetopause was in motion.
Title: The ultraviolet imager experiment on the Swedish
Viking satellite - Contributions to auroral physics
Authors: Cogger, L. L.; Murphree, J. S.; Elphinstone, R. D.;
Hearn, D. J.; King, R. A.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada), AC(Calgary, University,
Canada), AD(Calgary, University, Canada),
AE(Calgary, University, Canada)
Journal: Canadian Journal of Physics (ISSN 0008-4204), vol.
69, Aug.-Sept. 1991, p. 1032-1039. Research
supported by NSERC.
Publication Date: 09/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ZONES, SATELLITE-BORNE INSTRUMENTS,
ULTRAVIOLET PHOTOMETRY, IMAGING TECHNIQUES, POLAR
SUBSTORMS, SWEDISH SPACE PROGRAM, VIKING SPACECRAFT
Bibliographic Code: 1991CaJPh..69.1032C
Abstract
The ultraviolet imager on board the Swedish Viking satellite was
designed to provide real-time monitoring of the auroral distribution
from space. This objective was achieved over the nominal lifetime of
the satellite, March-December, 1986 during which period approximately
45,000 auroral images were acquired. A number of technical and
operational innovations have resulted in a rich data base for studies
of auroral and magnetospheric processes. Some of the significant
scientific advances that have resulted from the investigation of the
temporal and spatial development of the auroral distribution include
observations of rapid changes of dayside aurora, the effects of this
distribution due to the interplanetary magnetic field, and more
detailed knowledge of the substorm process. The utilization of models
of the earth's magnetic field to map auroral signatures to the
corresponding magnetospheric regions has led to an increased
understanding of the mechanisms associated with the large-scale auroral
distribution.
Title: Response of the dayside auroral and electrodynamic
processes to variations in the interplanetary
magnetic field
Authors: Ohtani, S.; Elphinstone, R. D.; Troshichev, O. A.;
Yamauchi, M.; Blomberg, L.; Zanetti, L. J.;
Potemra, T. A.
Journal: Journal of Geophysical Research, Volume 102, Issue
A10, p. 22247-22260 (JGR Homepage)
Publication Date: 09/1997
Origin: AGU
AGU Keywords: Atmospheric Composition and Structure: Airglow and
aurora, Ionosphere: Auroral ionosphere,
Magnetospheric Physics: Auroral phenomena,
Magnetospheric Physics: Solar wind/magnetosphere
interactions
Abstract Copyright: (c) 1997: American Geophysical Union
DOI: 10.1029/97JA01907
Bibliographic Code: 1997JGR...10222247O
Abstract
The response of the dayside auroral and electrodynamic processes to
variations in the interplanetary magnetic field (IMF) is examined with
multi-instrument data from the Viking and DMSP-F7 satellites as well as
ground magnetometer data. The event selected, which occurred on October
5, 1986, was previously identified as a high-latitude dayside form by
Murphree and Elphinstone [1988]. IMF BY was positive during
most of the Viking auroral UV observation, whereas IMF BZ
made a transient southward excursion, followed by a sharp increase to
+8nT. The results are summarized as follows: (1) There were two auroral
belts extending westward from the early afternoon sector. The
equatorward belt was persistent throughout the event and was embedded
in the CPS/BPS precipitation region, whereas the poleward belt was in
the open field line region and was associated with northward IMF BZ.
(2) A new auroral spot emerged in the afternoon sector just poleward of
the previously active region, delayed 10 min from the sudden increase
in IMF BZ. This time lag is ascribed to the travel time of
the new IMF orientation from the subsolar point to a solar
wind-magnetosphere interaction site tailward of the dayside cusp, as
well as to the response time of the dayside auroral acceleration
process. (3) The new auroral activity expanded both eastward and
westward during the first few minutes and then expanded primarily
westward across the noon meridian, forming the poleward belt. The speed
of the westward extension in the second phase was comparable to the
speed of the ionospheric convection. (4) The dayside auroral process
has a finite decay constant, which is inferred to be at least 10 min.
(5) The response time of the midday ionospheric convection to IMF
variations is estimated to be a few to several minutes.
Title: Intense growth phase events of substorms
Authors: Shue, J.-H.; Kamide, Y.; Elphinstone, R. D.;
Nishitani, N.
Journal: Journal of Geophysical Research, Volume 105, Issue
A3, p. 5357-5372 (JGR Homepage)
Publication Date: 03/2000
Origin: AGU
AGU Keywords: Ionosphere: Auroral ionosphere, Ionosphere: Current
systems, Ionosphere: Ionosphere/magnetosphere
interactions, Ionosphere: Ionospheric dynamics
Abstract Copyright: (c) 2000: American Geophysical Union
DOI: 10.1029/1999JA900454
Bibliographic Code: 2000JGR...105.5357S
Abstract
Over the past few decades, several events of the intense growth phase
preceding the expansion onset of substorms were reported. We reexamine
these events using an extensive set of data, including ground-based
magnetograms at auroral latitudes, solar wind data from the Wind and
IMP 8 satellites, and auroral UV images from the Polar and Viking
satellites. Magnetograms show that the intense auroral electrojet is
located in the early morning sector during these events. A common
feature among the corresponding solar wind conditions for these events
is the existence of a period of southward interplanetary magnetic field
(IMF) preceded by a prolonged northward IMF. This intense growth phase,
however, seems to be independent of the IMF By polarity.
Enhanced auroras in the early morning sector appear during the growth
phase. These auroras are consistent with relatively large geomagnetic
disturbances during these events, indicating that enhanced
conductances, combined with enhanced electric field caused by southward
IMF, play an important role in the auroral electrojet during these
intense growth-phase events.
Title: Mapping of the statistical auroral distribution into
the magnetosphere
Authors: Feldstein, Y. I.; Elphinstone, R. D.; Hearn, D. J.;
Murphree, J. S.; Cogger, L. L.
Journal: Canadian Journal of Physics. Vol. 72, p.266
Publication Date: 00/1994
Origin: ADS
Bibliographic Code: 1994CaJPh..72..266F
Abstract
Not Available
Title: Auroral dynamics and its relationship to high
altitude observations and processes (Invited)
Authors: Elphinstone, R. D.; et al.
Journal: International Conference on Substorms, Proceedings
of the 3rd International Conference held in
Versailles, 12-17 May 1996. Edited by E.J. Rolfe
and B. Kaldeich. ESA SP-389. Paris: European Space
Agency, 1996., p.3
Publication Date: 10/1996
Origin: ADS
Bibliographic Code: 1996icss.conf....3E
Abstract
Not Available
Title: Dayside aurora poleward of the main auroral
distribution: Implications for convection and
mapping
Authors: Elphinstone, R. D.; Hearn, D. J.; Murphree, J. S.
Journal: Physical Signatures of Magnetospheric Boundary Layer
Processes. Proceedings of the NATO Advanced Research
Workshop on Physical Signatures of Magnetospheric
Boundary Layer Processes, held May 9-14, 1993, in
H?efoss, Norway. Edited by Jan A. Holtet and Alv
Egeland. A C. I. P. Catalogue record for thei book
is available from the Library of Congress. ISBN
0-7923-27632. Published by Kluwer Academic
Publishers, Dordrecht, The Netherlands, 1994, p.189
Publication Date: 00/1994
Origin: ADS
Bibliographic Code: 1994psmb.conf..189E
Abstract
Not Available
Title: Some UV Dayside Auroral Morphologies
Authors: Elphinstone, R. D.; Hearn, D. J.; Murphree, J. S.;
Cogger, L. L.; Johnson, M. L.; Vo, H. B.
Journal: Auroral Plasma Dynamics, Geophysical Monograph 80.
Edited by Robert L. Lysak. Washington, DC: American
Geophysical Union, 1993., p.31
Publication Date: 00/1993
Origin: ADS
Bibliographic Code: 1993apd..book...31E
Abstract
Not Available
Title: Simultaneous observations of auroras in the northern
and southern polar caps
Authors: Zverev, V. L.; Starkov, G. V.; Vorob'ev, V. G.;
Leont'ev, S. V.; Fel'Dshtejn, Ya. I.; Elphinstone, R. D.;
Murphree, J. S.; Cogger, L. L.
Affiliation: AA(RAN, Polyarnyj Geofizicheskij Inst., Apatity,
Russia), AB(RAN, Polyarnyj Geofizicheskij Inst.,
Apatity, Russia), AC(RAN, Polyarnyj Geofizicheskij
Inst., Apatity, Russia), AD(RAN, Polyarnyj
Geofizicheskij Inst., Apatity, Russia), AE(IZMIRAN,
Troitsk, Russia), AF(Calgary Univ., Canada),
AG(Calgary Univ., Canada), AH(Calgary Univ., Canada)
Journal: Geomagnetizm i Aehronomiya (ISSN 0016-7940), vol.
32, no. 5, p. 62-70.
Publication Date: 10/1992
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAL ARCS, MAGNETIC STORMS, POLAR CAPS, SATELLITE
OBSERVATION, INTERPLANETARY MAGNETIC FIELDS,
MAGNETOACTIVITY, VIKING SPACECRAFT
Bibliographic Code: 1992Ge&Ae..32...62Z
Abstract
The positions of discrete auroral forms in the northern and southern
polar caps are compared for four time intervals. UV Viking-satellite
data were used for the northern polar cap, while all-sky-camera data
from the Vostok station were used for the southern polar cap. It is
shown that the discrete auroral forms can appear in the same time
sector, can be located symmetricaly with respect to the midday/midnight
line, or can appear only in one hemisphere.
Title: Particle precipitation dynamics in the polar cap
during an SC - Investigation of a specific event
Authors: Shumilov, O. I.; Raspopov, O. M.; Kasatkina, E. A.;
Elphinstone, R. D.; Creutzberg, F.
Affiliation: AA(AN SSSR, Poiarnyi Geofizicheskii Institut,
Apatity, USSR), AB(AN SSSR, Poiarnyi Geofizicheskii
Institut, Apatity, USSR), AC(AN SSSR, Poiarnyi
Geofizicheskii Institut, Apatity, USSR), AD(Calgary,
University, Canada), AE(National Research Council of
Canada, Herzberg Institute of Astrophysics, Ottawa)
Journal: Geomagnetizm i Aeronomiia (ISSN 0016-7940), vol. 31,
July-Aug. 1991, p. 591-600. In Russian.
Publication Date: 08/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: GEOMAGNETIC TAIL, MAGNETIC STORMS, PARTICLE
PRECIPITATION, POLAR CAPS, SOLAR TERRESTRIAL
INTERACTIONS, EARTH MAGNETOSPHERE, KELVIN-HELMHOLTZ
INSTABILITY, SOLAR WIND, SUDDEN STORM COMMENCEMENTS
Bibliographic Code: 1991Ge&Ae..31..591S
Abstract
The paper presents an investigation of physical processes in the
morning-evening sector of the polar cap and neighboring regions of the
auroral zone associated with the sudden storm commencement on Jan. 13,
1988 at 23.30 UT. Ground-based data indicate SCA-type absorption in the
auroral zone (Phi prime = 74 deg). Also established is SC propagation
into the magnetotail with velocities in the 750-1400 km/s range.
Title: The contribution of the boundary layer EMF to
magnetospheric substorms
Authors: Lundin, R.; Sandahl, I.; Woch, J.; Elphinstone, R.
Affiliation: AA(Calgary Univ., Alberta), AB(Calgary Univ.,
Alberta), AC(Calgary Univ., Alberta), AD(Calgary
Univ., Alberta)
Journal: Presented at Chapman Conference on Magnetospheric
Substorms, Hakone, Japan, 3-7 Sep. 1990
Publication Date: 01/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: BOUNDARY LAYERS, ELECTROMOTIVE FORCES, MAGNETIC
STORMS, MAGNETOSPHERIC INSTABILITY, SOLAR
TERRESTRIAL INTERACTIONS, AURORAS, CURRENT SHEETS,
DIURNAL VARIATIONS, ION INJECTION, IONOSPHERIC
CONDUCTIVITY, MAGNETIC FIELDS
Bibliographic Code: 1991masu.conf....3L
Abstract
The neutral line and boundary layer models to explain the triggering of
substorms are discussed based on the EMF (Electromotive force) produced
in the Low Latitude Boundary Layer (LLBL) as consequence of massive
solar wind plasma injection there. The hypothesis stems from recent
observations that the dayside oval is persistently active while the
nightside oval is only temporarily active. Region 1 current system is
argued to be divisable into two partial current circuits. One circuit,
entirely coupled to the LLBL, is related to the continuously active
dayside oval in the cleft region. The other circuit, connected to the
nightside oval and the tail current sheet, can be considered a
diversion or a tail route for currents driven by the LLBL. The
advantage with the current concept proposed is that it allows for both
a driven and loading/inloading mechanism for substorms. Auroral break
up is in this model a consequence of enhanced currents, induced by
solar wind pressure variations within the LLBL dynamo, that has reached
nightside magnetic field lines of enhanced ionospheric conductivity.
The model also allows for the development of tail plasmoids, generally
assumed to be the consequence of a current diversion instability within
the nightside current wedge.
Title: As the worm turns: Implications of bioturbation on
source rocks of the Horn Valley Siltstone
Authors: Elphinstone, Robyn; Gorter, John D.
Affiliation: AA(Petroz N.L., Perth, Australia), AB(Petroz N.L.,
Perth, Australia)
Journal: In its Geological and Geophysical Studies in the
Amadeus Basin, Central Australia, Bulletin 236 p
317-332 (SEE N91-27647 19-46)
Publication Date: 00/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: FOSSILS, GEOCHEMISTRY, LITHOLOGY, MARINE BIOLOGY,
MARINE ENVIRONMENTS, ORGANISMS, PALEONTOLOGY, ROCKS,
SEDIMENTS, VALLEYS, CORES, DECOMPOSITION, DOLOMITE
(MINERAL), GAMMA RAYS, LIMESTONE, OCEAN BOTTOM,
ORGANIC MATERIALS, SHALES, WELLS
Bibliographic Code: 1991ggsa.rept..317E
Abstract
The Horn Valley Siltstone was subdivided into ten informal members, HV1
(lowermost) to HV10, which reflect vertical lithofacies variations in a
shallow marine shelf environment. The members were defined primarily
from fully cored wells combined with gamma ray, sonic and density logs.
Sedimentological and paleontological information, such as the presence
or absence of body fossils, mode of preservation, species associations
within groups of fossils, presence or absence of bioturbation (trace
fossils), lithology, and bedding type, were also used. It can be
inferred that the amount and composition of organic matter preserved in
the sediment was determined largely by the concentration of oxygen in
the bottom water and the extent to which the sediment was disrupted by
burrowing organisms, because burrowing and scavenging activities of
benthic organisms are controlled by the concentration of oxygen in the
bottom water. Organic geochemical data from Tempe Vale 1 and Tent Hill
1 were used to confirm these facies variations. The Horn Valley
Siltstone was deposited during a transgressive-regressive episode and
the organic-rich sediments, those with high TOC values (HV5, HV6, HV7),
were buried rapidly. This allowed the exceptional preservation of
organic matter and reduced its residence time in zones of bioturbation
and oxic decomposition. This may have been linked to upwelling along
the Central Ridge. The bioclastic limestone and dolomite interbedded
with the bioturbated shale and siltstone (e.g., HV3, HV9) were probably
deposited within well oxygenated and shallower shelf settings, and were
moved by density currents into deeper water.
Title: Late Proterozoic and early Palaeozoic palaeontology
and biostratigraphy of the Amadeus Basin
Authors: Shergold, J. H.; Elphinstone, Robyn; Laurie, J. R.;
Nicoll, Robert S.; Walter, M. R.; Young, G. C.;
Zang, Wenlong
Affiliation: AA(Australian National Univ., Canberra.),
AB(Australian National Univ., Canberra.),
AC(Australian National Univ., Canberra.),
AD(Australian National Univ., Canberra.),
AE(Australian National Univ., Canberra.),
AF(Australian National Univ., Canberra.),
AG(Australian National Univ., Canberra.)
Journal: In its Geological and Geophysical Studies in the
Amadeus Basin, Central Australia, Bulletin 236 p
97-111 (SEE N91-27647 19-46)
Publication Date: 00/1991
Category: Geophysics
Origin: STI
NASA/STI Keywords: AUSTRALIA, CRATONS, FOSSILS, PALEONTOLOGY,
PRECAMBRIAN PERIOD, STRATIGRAPHY, STRUCTURAL BASINS,
VERTEBRATES, MINERAL DEPOSITS, MODELS
Bibliographic Code: 1991ggsa.rept...97S
Abstract
The extent of palaeontological and biostratigraphic research undertaken
during the most recent phase of Bureau of Mineral Resources (BMR)
activity in the Amadeus Basin. Coordinated individual contributions are
presented on the basis of the systematic palaeontological description
and evaluation of the Late Proterozoic acritarchs, Early Cambrian
inchofossils, Early Cambrian phosphatic and phosphatized macrofaunas,
Late Cambrian and Early Orovician trilobites and condonts, and
Ordovician and Devonian macro- and micro-vertebrates. As a result,
biostratigraphic refinement of the Late Proterozoic-Early Cambrian Late
Cambrian-Early Ordovician, and Middle-Late Devonian intervals was made
possible, and represents a significant advance of knowledge. Refinement
of the Late Cambrian-Early Ordovician interval has led to the
recognition of previously unknown stratigraphic breaks of consequence
to event stratigraphy and to the development of palaeogeographic models
which have a wider application in other Australian cratonic basins.
Title: Association of an auroral surge with plasma sheet
recovery and the retreat of the substorm neutral
line
Authors: Hones, E. W.; Elphinstone, R.; Murphree, J. S.;
Galvin, A. B.; Heinemann, N. C.
Affiliation: AA(Boston Coll., Chestnut Hill, MA.), AB(Boston
Coll., Chestnut Hill, MA.), AC(Boston Coll.,
Chestnut Hill, MA.), AD(Boston Coll., Chestnut Hill,
MA.), AE(Boston Coll., Chestnut Hill, MA.)
Journal: Presented at the Chapman Conference on
Magnetospheric Substorms, Hakone, Japan, 3-7 Sep.
1990
Publication Date: 00/1990
Category: Geophysics
Origin: STI
NASA/STI Keywords: AURORAS, EARTH MAGNETOSPHERE, MAGNETIC FIELDS,
PLASMA LAYERS, STORMS, ELECTRONS, SURGES
Bibliographic Code: 1990masu.conf....3H
Abstract
One of the periods being studied is the interval 0000-1200 UT on May 3,
1986, designated Event 9C. A well-defined substorm, starting at 0919
UT, was imaged by both the Dynamics Explorer 1 (DE 1) 1 over the
Southern Hemisphere and Viking over the Northern Hemisphere. The images
from Viking, at 80-second time resolution, showed a surge-like feature
forming at about 0952 UT at the poleward edge of the late evening
sector of the oval. The feature remained relatively stationary until
about 1000 UT when it seemed to start advancing westward. ISEE 1 and 2
were closely conjugate to the surge as mapped from both the Defense
Meteorological Satellite Program (DMSP) and Viking images. We conclude
that the plasma sheet recovery was occasioned by the arrival at ISEE
1,2 of a westward traveling wave of plasma sheet thickening, the wave
itself being formed by westward progression of the substorm neutral
line's tailward retreat. The westward traveling surge was the auroral
manifestation of this nonuniform retreat of the neutral line. We
suggest that the upward field aligned current measured by DMSP F7 above
the surge head was driven by plasma velocity shear in the plasma sheet
at the duskward kink in the retreating neutral line. By analogy with
this observation we propose that the westward traveling surges and the
current wedge field aligned currents that characterize the expanding
auroral bulge during substorm expansive phase are manifestations of
(and are driven by) velocity shear in the plasma sheet near the ends of
the extending substorm neutral line.
Title: Study of a substorm on May 4, 1986
Authors: Hones, E. W.; Craven, J. D.; Frank, L. A.; Galvin, A. B.;
Murphree, J. S.; Elphinstone, R. D.; Elphic, R. C.
Affiliation: AA(California Univ., Los Angeles.), AB(California
Univ., Los Angeles.), AC(California Univ., Los
Angeles.), AD(California Univ., Los Angeles.),
AE(California Univ., Los Angeles.), AF(California
Univ., Los Angeles.), AG(California Univ., Los
Angeles.)
Journal: Presented at the 27th Plenary Meeting of COSPAR,
Espoo, Finland, 18 Jul. 1988
Publication Date: 00/1988
Category: Geophysics
Origin: STI
NASA/STI Keywords: EARTH MAGNETOSPHERE, GEOMAGNETIC TAIL, MAGNETIC
STORMS, AURORAL ELECTROJETS, AURORAS, SOLAR WIND,
SUN
Bibliographic Code: 1988cosp.meetQ....H
Abstract
A substorm on May 4, 1986, midway through the PROMIS campaign of
coordinated data acquisition, was uniquely well documented. Both in its
aspects at earth and in its magnetotail aspects. The expansive phase
onset was imaged by the Viking satellite at 20-second time resolution.
Most of the expansive phase was also imaged by DE 1 at 6-minute time
resolution. ISEE 1 and 2 were near the tail's axis 18.5 R sub e from
earth operating at high data rate and data were recorded by several
geosynchronous satellites. This multi-satellite study provides evidence
that the active substorm aurora occurs at the feet of field lines that
map to a magnetic X-line in the near tail. The longitudinal extension
of the aurora during a substorm is associated with cross-rail
lengthening of the near-earth neutral line. The concept of the poleward
leap of the auroral electrojet (and the auroras) as the culminating
feature of the expansive phase finds further support in these data.
Title: Correlative studies using the Viking imagery
Authors: Murphree, J. S.; Elphinstone, R. D.
Affiliation: AA(Calgary, University, Canada), AB(Calgary,
University, Canada)
Journal: (COSPAR and SCOSTEP, Plenary Meeting, 27th,
Symposium on Multipoint Magnetospheric Measurement,
8th, Espoo, Finland, July 18-29, 1988) Advances in
Space Research (ISSN 0273-1177), vol. 8, no. 9-10,
1988, p. 9-15, 17-19. (AdSpR Homepage)
Publication Date: 00/1988
Category: Geophysics
Origin: STI
NASA/STI Keywords: EARTH MAGNETOSPHERE, SATELLITE IMAGERY, SCIENTIFIC
SATELLITES, SWEDISH SPACE PROGRAM, AURORAL ZONES,
CORRELATION, INTERPLANETARY MAGNETIC FIELDS,
MAGNETIC FIELD RECONNECTION, POLAR SUBSTORMS
DOI: 10.1016/0273-1177(88)90108-1
Bibliographic Code: 1988AdSpR...8....9M
Abstract
Observations made with the UV Imager onboard the Viking satellite
provide an ideal means whereby diverse data sets can be correlated
together into the global context of magnetospheric processes. Substorm
observations reveal the frequent occurrence on very short time scales
(less than a minute) of extended arc brightenings during the early
recovery phase of substorms. These brightenings are accompanied by the
formation of multiple spirals due probably to instabilities operating
along the field lines connecting the source region for the particles
with the ionosphere. On the dayside, by comparing the UV observations
with Interplanetary Magnetic Field data, it is found that during
positive B(z) and away sector configurations, localized regions of
emission can propagate either duskward or dawnward depending on the
sign of B(v). In the context of current merging/reconnection theories,
it seems plausible that these motions are the ionospheric signature of
the drift of newly merged flux tubes.
Title: Satellite observations of 557.7 NM airglow as a
diagnostic technique to study the dynamics of the
lower thermosphere
Authors: Cogger, L. L.; Elphinstone, R.; Murphree, J. S.
Affiliation: Calgary Univ. (Alberta).
Journal: In International Council of Scientific Unions
Handbook for MAP, Vol. 18 1 p (SEE N86-27719 18-46)
Publication Date: 12/1985
Category: Geophysics
Origin: STI
NASA/STI Keywords: AIRGLOW, ATMOSPHERIC COMPOSITION, OXYGEN, SATELLITE
OBSERVATION, THERMOSPHERE, ANNUAL VARIATIONS,
ATMOSPHERIC MODELS, PHOTOCHEMICAL REACTIONS
Bibliographic Code: 1985icsu...18T....C
Abstract
Photometric observations of the airglow limb at 557.7 nm have been made
from the ISIS 2 satellite since 1971. From an analysis of 32,000
airglow limb observations obtained during the first two years of
operation, the major temporal and spatial characteristics of the night
airglow have been identified. Maxima occur in mid-October and mid-April
at all latitudes. There is a marked variation with latitude during the
equinox periods, with peak intensities near 35 degrees in autumn and
near 25 degrees in spring. It is possible to gain considerable insight
into the behavior of the lower thermosphere by combining the airglow
observations with a simple model of the photochemical and dynamical
processes. In this way a pattern of the latitude and temporal variation
of atomic oxygen concentration at the peak of the layer as well as the
eddy diffusion in this altitude region have been inferred. The
concentration of atomic oxygen shows midlatitude peaks near equinox,
and minima about one month after solstice. Average values at
midlatitudes are about 1.3 times those at the equator. The amplitude of
the semiannual component is about 20% of the mean value at 35 degrees
as compared to 10% at the equator, and the amplitude of 12-month
component is about 12% at 35 deg and 5% at the equator. The semiannual
component has a minimum that occurs approximately 3 weeks (plus or
minus) after solstice at all latitudes, while the 12-month component
peaks in the summer hemisphere at solstice (plus or minus 2 months).
Title: Satellite observations of 557.7 nm airglow as a
diagnostic technique to study the dynamics of the
lower thermosphere
Authors: Cogger, L. L.; Elphinstone, R.; Murphree, J. S.
Journal: Middle Atmosphere Program. Handbook for MAP. Volume
14: URSI/SCOSTEP Workshop on Technical Aspects of
MST Radar, Workshop held in Urbana, Ill., 22-25 May
1984. Edited by S.A. Bowhill and Belva Edwards,
December, 1984., p.326
Publication Date: 12/1984
Origin: ADS
Bibliographic Code: 1984maph...14..326C
Abstract
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