The Los Alamos MPA Data Set:
State of the Magnetosphere During the
November 1993 Storm
The Magnetospheric Plasma Analyzer (MPA) instruments observe 1 eV - 40 keV ions and electrons from three satellites in geosynchronous orbit. At the time of the storm, the satellites were at geographic longitudes of -165=B0, -37=B0, and +70=B0, i.e., near the Alaska, Greenland, and Novaya Ze= mlya meridians. Throughout the course of the November 1993 storm, MPA identified various states and dynamics of the middle magnetosphere. During the two days prior to the storm the plasmasphere was built up, ion pressure in the ring current was quite low, and normal field stretching existed on the nightside. These are all characteristic signatures of a quiet magnetosphere. The penetrating background, due to energetic electrons, was low. During the positive-Dst interval on November 3rd, the plasmasphere remained built up and the nightside geomagnetic field was uncharacteristically dipolar (instead of tail-like). At roughly 7:00 UT during this interval on the 3rd, a very large anisotropy (Tperp > Tparallel) in the ring-current ions developed, followed by a somewhat smaller electron anisotropy in the plasma sheet. At about 18:00 UT, the plasmasphere disappeared from the nightside geosynchronous satellites but remained visible on the dayside; this is indicative of the outer plasmasphere being convected sunward, toward the dayside neutral line. At about this time, high-density ion and electron plasma sheets appeared. During the drop in Dst, at around 0:00 UT on the 4th, the geosynchronous satellite near local noon encountered magnetosheath and boundary layer plasmas indicating that the magnetopause was inside of geosynchronous orbit on the dayside. The penetrating background remained low. During the first day of the storm, both electron and ion pressures were very high, owing to the very high densities of the electron and ion plasma sheets. Thereafter, the plasma sheet densities and pressures were normal. The penetrating background finally began to increase at roughly 3:00 UT on the 5th, peaked early on the 8th, and decreased thereafter. MPA observations detail a strong and long-lasting impact on the magnetosphere due to the November 1993 storm.
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