Particle Acceleration at the Geomagnetic Cusps - Myth or Reality

There has been a long standing dispute on the origin of accelerated particles observed at the Earth's magnetic cusps. Observations show the presence of an energetic particle population in the vicinity of these cusps, however there are various hypotheses on the origin and the acceleration mechanism. While some believe that these particle are indeed accelerated locally in the cusp magnetic field geometry another hypothesis assumes that these particle are accelerated at the quasi-parallel bow shock of the magnetosphere and are only found at the cusp if this bow shock region is magnetically connected to the cusp. Similarly there are several hypotheses on a possible local acceleration mechanism with the dominant idea of acceleration by a turbulent wave field. The presentation summarizes observations and arguments accelerated particle populations in the cusps and will discuss first results of simulations of particle dynamics in a cusp geometry.