Plasma temperature distributions in the heliosheath

Abstract

Voyager 2 crossed the termination shock (TS) in August 2007 and began observations of the heliosheath. We present the first 400 days of heliosheath plasma data and propose a consistent picture of the energy flow across the TS. Roughly 15% of the plasma flow energy lost at the shock heats the thermal ions and most of the rest of this energy heats the pickup ions. The pickup ions make up roughly 20% of the sheath plasma and have energies of about 6 keV in the heliosheath, consistent with STEREO observations. Relative standard deviations of the proton temperature in the upstream solar wind and in the heliosheath are similar, but this similarity is probably accidental since the temperatures are strongly modified at the termination shock. The temperature fluctuations in the heliosheath may be derived from changes in the TS speed and/or temporal changes in the TS structure. Copyright 2008 by the American Geophysical Union.