Characteristics of Suprathermal Electron Bursts Observed by the DMSP-F6/F7 Satellites in the Diffuse Aurora Region

Abstract

The particle data of the DMSP-F6 and -F7 satellites show the presence of suprathermal electron bursts in the diffuse aurora region. These bursts are characterized by intense (∼10⁸-10⁹ (cm²sr sec)^-1), low energy (∼100-500 eV), and localized (∼20-30 km at satellite altitude h ≅ 830 km) electron precipitation. Simultaneous magnetic field data from the DMSP-F7 satellite show that these bursts are often, but not always, accompanied with intense (few μAm^-2), small-scale (only few tens of km at satellite altitude) upward field-aligned currents. The bursts are observed from 19 h to 11 h MLT through midnight during the maximum to recovery phase of substorm. These bursts are less likely to be observed during geomagnetic storms than during times of isolated substorms. These results suggest that suprathermal electron bursts are generated by localized heating of ionospheric electrons which flow out from the ionosphere toward the magnetosphere during substorm.