Energetic electrons in the exterior cusp: identifying the source

Abstract. A case study is presented to test the role several different sources may play in populating the exterior cusp with energetic (E>40 keV) electrons. The properties of the electrons measured in the exterior cusp are compared with the expected signatures of three sources in order to weigh the role each source may contribute in populating this region. The potential sources probed are: (1) solar energetic electrons entering the cusp from the solar wind; (2) an equatorial magnetospheric source with particles drifting to high latitudes on the dayside; and (3) a local source accelerating the electrons in situ. From the observations it is likely that local acceleration is the primary source of the energetic electrons in the exterior cusp during this event.