Modeling of the outer electron belt during magnetic storms

The flux dropout of relativistic electrons in the earth's outer radiation b elt, during the main phase of the 26 March 1995 magnetic storm is examined. Outer belt measurements by the Radiation Environment Monitor, REM aboard t he STRV-1b satellite are presented to characterize this dropout. In order t o simulate the dynamics of the electron belt during the storm main phase a particle tracing code was developed which allows to trace the trajectories of equatorially mirroring electrons in a dynamic magnetospheric electromagn etic field. Two simulations were performed in a non-stationary magnetic fie ld, one taking only the induced electric held into account (fully adiabatic motion), and one with an additional non-stationary convection electric fie ld. The simulations show, that adiabatic deceleration can produce the obser ved count rate decrease and also the observed inward motion of the count ra te peak. The convection electric field causes diffusion, which can take par ticles from low L values out to the magnetopause and contribute to an addit ional loss of particles, which is suggested by the observations. (C) 1999 E lsevier Science Ltd. All rights reserved.