Cusp Region as Viewed by Energetic Electrons and Ions:A Statistical Study Using Cluster Rapid Data

In this paper, we present statistical results from the energetic electron and ion data set obtained by RAPID/Cluster. The energy range for ions extends from 30 to 1500 keV and for electrons between 20 to 400 keV. Data set obtained by Cluster from January 1 to June 30, 2001 are used to study the extension of the cusp in magnetic local time, invariant latitude, and its dependence on geomagnetic activity, e.g. Dst, Kp indices and the solar wind and Interplanetary Magnetic Field (IMF) conditions. Furthermore, the relation between the energetic particles and local plasma and magnetic field is explored in detail. Frequently the energetic particles provide the clearest/cleanest indication of the boundaries of the cusp region.Energetic ions are essentially present on each pass through this region but the energetic electron behavior in the cusp region was significantly more structured and variable than the ions. The asymmetry between south and north cusp was also studied and will be discussed.