Properties and Possible Causes of Low Latitude Broadband Accelerated Electron Events During Large Storms From FAST and Altitude Dependence of PSBL Alfven Waves From Polar

A variety of phenomena which occur during large geomagnetic storms (DST<-75 nT) are not yet fully understood. One such phenomenon, which affects ionospheric conditions and may be useful as a diagnostic for processes occurring at ~3-6 Re, is the occurrence of low latitude (ILat<65) broadband accelerated electron events observable at altitudes of ~2000-4000 km by the FAST satellite. Results of an initial study of 3+ years of FAST data indicate that such electrons are observed in ~6% of the low latitude, nightside (21- 03 MLT) FAST data during large storms versus <~1% during non-storm times. Individual storms have observed occurrence probabilities as high as 24%. Although properties of the events, and thus likely causes, vary, many events are accompanied by particle distributions and wave signatures that are similar to those observed during Alfvén-wave accelerated electron events on the plasma sheet boundary layer (PSBL). Alfvén- wave acceleration of electrons on the PSBL has been and continues to be well studied. Results of a recent study of PSBL Alfvén-wave events observed with Polar that may provide additional insight will also be discussed. That study compares altitude dependencies of wave properties at ~3-9 Re and differences in these dependencies between major storm and non-storm events.