LARGE-AMPLITUDE ELECTRIC AND MAGNETIC-FIELD SIGNATURES IN THE INNER MAGNETOSPHERE DURING INJECTION OF 15 MEV ELECTRON-DRIFT ECHOES

Electric and magnetic fields were measured by the CRRES spacecraft at an L-value of 2.2 to 2.6 near 0300 magnetic local time during a strong storm sudden commencement (SSC) on March 24, 1991. The electric field signature ai the spacecraft at the time of the SSC was characterized by a large amplitude oscillation (80 mV/m peak to peak) with a period corresponding to the 150 second drift echo period of the simultaneousl y observed 15 MeV electrons. Considerations Of previous statistical st udies of the magnitude of SSC electric and magnetic fields versus loca l time and analysis of the energization and cross-L transport of the p articles imply the existence of 200 to 300 mV/m electric fields over m uch of the dayside magnetosphere. These observations also suggest that the 15 MeV drift echo electrons were selectively energized because th eir gradient drift velocity allowed them to reside in the region of st rong electric fields for the duration of the accelerating phase of the electric field.