DMSP-F2 Observations of Cusplike Electron Precipitation Regions during the September 19–21, 1977 Event

The differential particle spectrum of electrons between 50 eV and 20 keV, as measured by the electrostatic analyser on DMSP-F2, is used to identify regions of precipitation in the earth’s polar regions above 800 km altitude. A typical cusplike spectrum is defined by analysis of the DMSP data, compared with published data, and used to locate regions of cusplike precipitation. A comparison between the September 19–21, 1977 stormtime location of such regions and the quiet-time location is discussed. In general, the region of cusplike precipitation is significantly displaced equatorward from its quiet-time location.