Uncertainties in the heliosheath ion temperatures

Abstract

Abstract. The Voyager plasma observations show that the physics of the heliosheath is rather complex and that the temperature derived from observation particularly differs from expectations. To explain this fact, the temperature in the heliosheath should be based on κ distributions instead of Maxwellians because the former allows for much higher temperature. Here we show an easy way to calculate the κ temperatures when those estimated from the data are given as Maxwellian temperatures. We use the moments of the Maxwellian and κ distributions to estimate the κ temperature. Moreover, we show that the pressure (temperature) given by a truncated κ distribution is similar to that given by a Maxwellian and only starts to increase for higher truncation velocities. We deduce a simple formula to convert the Maxwellian to κ pressure or temperature. We apply this result to the Voyager 2 observations in the heliosheath. Keywords. Space plasma physics (kinetic and MHD theory)