Fluxes of 40–500 keV electrons at the geostationary orbit without strong geomagnetic disturbances, and interplanetary medium parameters

The study is focused on 40–500 keV electron flux enhancements at the geostationary orbit, which occur without strong geomagnetic disturbances. We use data on the differential-energy electron flux recorded by the magnetospheric satellite GOES-15. Electron flux enhancements occurring without magnetic storms and strong substorms are selected for analysis. The superposed epoch method is employed to examine interplanetary medium and solar wind parameters during the enhancement intervals, as well as during the preceding several hours, which are compared with intervals lacking enhancements but exhibiting similar geomagnetic and auroral activity indices. We also compare the energy spectra of electrons averaged over the selected event groups. We demonstrate that differences in solar wind speed are observed for at least 6 hours prior to the onset of enhancements, and the immediate precursor to the enhancement emerging 1–2 hours before a selected flux local maximum is a rise in solar wind dynamic pressure.