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Relativistic Electron Response
to the January 1997
Magnetic Cloud: Coordinated Observations from 12 Satellites
Key Data Sets
Polar/IPS Energetic Ions, LANL Geosynchronous
Energetic Particles, Polar/VIS Auroral Imager
Key Results
12 Satellites simultaneously measuring
the enhancement of relativistic electrons in the radiation belts while Wind
monitors upstream conditions
Contacts
Geoffrey D. Reeves, Los Alamos National
Lab., 505/665-3877, reeves@lanl.gov
More Information
Reeves, G. D., D. N. Baker, R. D. Belian,
J. B. Blake, T. E. Cayton, J. F. Fennell, R. H. W. Friedel, M. G. Henderson,
X. Li, M. M. Meier, T. G. Onsager, R. S. Selesnick, and H. E. Spence, Relativistic
Electron Response to the January 1997 Magnetic Cloud: Coordinated Observations
from 12 Satellites, IAGA General Assembly, Uppsala, Sweden, Aug. 5-15, 1997.
NASA Event Page: http://www-istp.gsfc.nasa.gov/istp/cloud_jan97/event.html
Media Coverage: http://www-spof.gsfc.nasa.gov/istp/cloud_jan97/media/
LANL News Bulletin: http://www.lanl.gov/projects/PA/News/012497.html#anchor263034
Abstract
On January 10 and 11, 1997 a CME-produced
magnetic cloud encountered the Earth's magnetosphere and produced a geomagnetic
storm. This storm has generated a lot of interest because it was exceptionally
well observed and because of its possible association with the loss of an
AT&T communications satellite. This study investigates the acceleration
of relativistic electrons in the radiation belts. The relativistic electron
response was being monitored by instruments on a remarkable constellation
of 12 satellites: 3 LANL geosynchronous, 2 GOES, 2 Aerospace HEO, and 3
GPS, as well as SAMPEX and POLAR. We present observations from those spacecraft
and examine the three- dimensional structure and dynamics the relativistic
electron event.
The magnetospheric response began in close association with the arrival of southward IMF. Injections of energetic particles (tens of keV) continued throughout the period of strong southward field. The fluxes of relativistic electrons(E>1MeV) showed two separate enhancements. The first enhancement began on January 10, was relatively abrupt, and lasted for approximately 24 hours. It appears to be associated with a strong compression of the magnetosphere which briefly drove the magnetopause inside geosynchronous orbit. We will examine whether this initial enhancement could be an adiabatic response to the magnetospheric compression. We will also examine the effect of the compression of the magnetopause to inside geosynchronous orbit and the possible effects of magnetopause drift shadowing. We will compare the first enhancement with the later enhancement which was more typical of the magnetospheric response to high speed streams: the fluxes gradually increased over several days following the passage of the cloud, with lower energy electron fluxes peaking first followed by the higher energy electron fluxes.
This event clearly illustrates the old adage that the whole is greater than the sum of its parts. The value of non-NASA satellites to the goals of ISTP is also self-evident. Without the geosynchronous, GPS, and HEO satellites this would be a 2-satellite study of the radiation belts. The philosophy behind ISTP was to put as many spacecraft as possible into key regions of the magnetosphere. The constellation illustrated above shows success and innovation on the part of the program office - not only in launching new satellites but in successfully leveraging data sets from non-NASA, programmatic missions to support the goals of ISTP. Although the results of this study are still being compiled the opportunities presented by this constellation, both for the January 1997 event and for others yet to come, are unprecedented.
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