SIMULATION OF THE PROMPT ENERGIZATION AND TRANSPORT OF RADIATION BELTPARTICLES DURING THE MARCH 24, 1991 SSC

We model the rapid (approximately 1 min) formation of a new electron r adiation belt at L congruent-to 2.5 that resulted from the Storm Sudde n Commencement (SSC) of March 24, 1991 as observed by the CRRES satell ite. Guided by the observed electric and magnetic fields, we represent the time-dependent magnetospheric electric field during the SSC by an asymmetric bipolar pulse that is associated with the compression and relaxation of the Earth's magnetic field. We follow the electrons usin g a relativistic guiding center code. The test-particle simulations sh ow that electrons with energies of a few MeV at L > 6 were energized u p to 40 MeV and transported to L congruent-to 2.5 during a fraction of their drift period. The energization process conserves the first adia batic invariant and is enhanced due to resonance of the electron drift motion with the time-varying electric field. Our simulation results, with an initial W-8 energy flux spectra, reproduce the observed electr on drift echoes and show that the interplanetary shock impacted the ma gnetosphere between 1500 and 1800 MLT.