HR: 1330h
AN: SH42A-0488    [PDF]
TI: Relativistic Electron Equatorial Phase Space Densities Gradients from 4 to 20 Re
AU: * Reeves, G D
EM: reeves@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D-466, Los Alamos, NM 87544 United States
AU: Taylor, M G
EM: mggtt@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D-466, Los Alamos, NM 87544 United States
AU: Friedel, R H
EM: friedel@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D-466, Los Alamos, NM 87544 United States
AU: Chen, Y
EM: cheny@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D-466, Los Alamos, NM 87544 United States
AB: A critical parameter for understanding radiation belt electron dynamics is the gradient in phase space density as a function of radius. Typically one wants to calculate phase space densities as a function of the adiabatic invariants of particle motion. The inaccuracies in calculation of the adiabatic invariants caused by inaccuracies in our global magnetic field models can be reduced if only 90 degree equatorial pitch angles are used (and the second invariant is zero). In this study we use the near-equatorial measurements from geosynchronous satellites along with the equatorial crossings of the GPS, POLAR, and Cluster spacecraft. GPS crosses the magnetic equator around L=4.5, Geosynchronous near L=6.6 and Cluster in the mid-tail, L=18-20. Previous studies that we have presented showed a strong PSD radial gradient inside geosynchronous orbit and a very weak radial gradient outside geosynchronous orbit. The inflection point in the gradient appears near the expected location of the trapping boundary and suggests that the gradients in the plasma sheet are quite weak. Our studies confirm the results of Green et al. suggesting the presence of a peak in phase space density in at least some events. In this study we extend previous work by examining a large number of equatorial measurements by all 4 sets of satellites over the years 1997 to 2002. In particular we concentrate on equatorial PSD measurements by POLAR. Because of the precession of the orbit, POLAR equatorial crossings range from L=4 to L=9 depending on the year of measurement. Therefore, in a statistical sense POLAR fills in the region of primary interest with an unprecedented density of equatorial PSD measurements. This statistical analysis shows the broad range of radiation belt dynamics and average profiles of radial gradients as a function of solar wind driving and geomagnetic conditions.
DE: 2720 Energetic particles, trapped
DE: 2730 Magnetosphere--inner
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting