Incoherent Scatter Radar Observations of Ionospheric Signatures of Cusp-Like Electron Precipitation.

Abstract

We present a case study of spatially and temporally coincident DMSP-F7 electron and ion precipitation measurements and Sondrestrom incoherent scatter radar observations of ionospheric plasma parameters. The particle flux data allow us to determine the boundaries between the magnetospheric regions central plasma sheet (CPS), plasma sheet boundary layer (PSBL), cusp proper, and plasma mantle (PM), mapped down to the DMSP orbit (835km altitude). The PSBL, cusp, and the equatorward section of the PM are characterized by intense low energy (<400eV) electron precipitation. The radar measured enhanced plasma density and elevated electron temperature at 350km altitude at the same invariant latitude interval where DMSP-F7 detected the intense low-energy electron flux. The ion temperature was unaffected, as were plasma density and electron and ion temperatures at 200km altitude. The plasma convection pattern inferred from radar Doppler shift measurements suggests that the heated electron cloud observed in the F region was locally produced by the soft electron precipitation in and near the cusp proper rather than convected into the radar field of view. This study demonstrates that soft electron precipitation, which is typical for magnetosheath-like plasma entry observed in particular in the cusp, can under certain conditions be identified by its thermal ionospheric plasma signatures.