FULLY ADIABATIC CHANGES IN STORM TIME RELATIVISTIC ELECTRON-FLUXES

It has been suggested that much of the drop and subsequent recovery of storm time relativistic electron fluxes at geosynchronous orbit can b e explained in terms of a fully adiabatic response (all three adiabati c invariants conserved) to magnetic field changes. To calculate this e ffect, we assume a prestorm electron flux distribution constructed fro m CRRES satellite data, we use modular magnetospheric magnetic field m odels to represent the magnetic field configuration before and during the storm, and we use Liouville's theorem to evolve the prestorm elect ron flux. In this work we focus on the important special case of equat orially mirroring electrons. During the main phase of a storm with a D st minimum of -100 nT we find that the fully adiabatic effect can caus e a flux decrease of up to 2 orders of magnitude, consistent with obse rved flux decreases. We also find that the magnitude of the fully adia batic flux decrease is larger for lower energies, again in agreement w ith observations. The contribution of prestorm electron fluxes to the recovery phase flux increase at synchronous orbit is expected to be sm all because of losses to the dawnside magnetopause. A comparison of fu lly adiabatic fluxes with measured electron fluxes for the November 2- 5, 1993, storm indicates that for this event the fully adiabatic effec t may be contributing to the observed decrease but that nonadiabatic e ffects are clearly important. Overall we conclude that the fully adiab atic effect can account for a significant fraction of observed flux de creases and that differences between the observed and the fully adiaba tic fluxes help to clarify when and where additional loss and source m echanisms exist.