PROGNOZ-10 ENERGETIC PARTICLE DATA - LEAKAGE FROM THE MAGNETOSPHERE VERSUS BOW SHOCK ACCELERATION

We present a case study and a statistical survey of Prognoz 10 energet ic particle and magnetic field observations from the solar wind to the magnetosphere. The results provide evidence for both Fermi accelerati on and leakage from the magnetosphere. Energetic ion (E > 15 keV) flux levels upstream of the bow shock and in the outer magnetosphere gener ally exceed those in the magnetosheath Energetic electrons rarely acco mpany ion fluxes in the outer magnetosheath and upstream of the bow sh ock, but commonly accompany those in the inner magnetosheath. Upstream flux levels increase as the interplanetary magnetic field (IMF) rotat es toward the bow shock normal, consistent with Fermi acceleration. Al though the north/south magnetosheath magnetic field orientation has no effect upon energetic particle flux levels in the outer magnetosheath , flux levels in the inner magnetosheath increase during periods of so uthward IMF. We interpret the results as indicating that Fermi acceler ation supplies most of the ions observed in the outer dayside magnetos heath but that leakage from the magnetosphere supplies most of the ion s observed in the inner magnetosheath.