Cluster-Polar Simultaneous Observations of Energetic Particles in the Plasma Sheet - Evidence for Radiation Belt Leakage?

Fortuitously Polar and Cluster orbits are close to co-planer. As one result, quite frequently Polar and Cluster s/c are near the magnetic equator and the same local time but they differ in radial distance by ~ 10 RE. In the magnetotail regions, a low flux of energetic electrons and ions, E > ~ 30 keV is routinely observed punctuated during a several hour period by short bursts of greatly enhanced particle intensities. These bursts are time coincident at Polar and Cluster and frequently are associated with a change in the magnitude/direction of the magnetic field at Polar. At these times Polar is near the trapping boundary. An obvious origin for these energetic particles is leakage from the radiation belts, with enhanced leakage occurring during re configurations of the geomagnetic field near the trapping boundary. It has long been speculated that these losses would result from a breakdown of adiabatic motion. An estimate for the loss rate from the radiation belts will be discussed.