Turbulent Heating of Jupiter's Middle Magnetosphere

Abstract

We give a possible explanation for the high ion temperatures of ~10 8 K measured in the middle magnetosphere of Jupiter. In the absence of a significant heat source, much lower temperatures are expected due to adiabatic cooling of the expanding cloud of plasma from the Io torus region of the magnetosphere. We show that the weak magnetohydrodynamic turbulent fluctuations observed in the middle magnetosphere dissipate energy at a rate that can account for the high ion temperatures. A simple estimate gives a turbulent heating rate of 2.5 × 10 7 K day -1 at a radial distance of around 20 Jupiter radii, where the turbulence maximizes. We present a one-dimensional radial temperature model and find a temperature profile in good agreement with the values observed by the Galileo spacecraft.