A Turbulent Heating Model Combining Diffusion and Advection Effects for Giant Planet Magnetospheres

The ion temperature of the magnetospheres of Jupiter and Saturn was observed to increase substantially from about 10 to 30 planet radii. Different heating mechanisms have been proposed to explain such observations, including a heating model for Jupiter based on MHD turbulence with flux-tube diffusion. More recently, an MHD turbulent heating model based on advection was shown to also explain the temperature increase at Jupiter and Saturn. We further develop this turbulent heating model by combining effects from both diffusion and advection. The combined model resolves the physical consistency requirement that diffusion should dominate over advection when the radial flow velocity is small and vice versa when it is large. Comparisons with observations show that previous agreements, using the advection only model, are still valid for larger radial distance. Moreover, the additional heating by diffusion results in a better agreement with the temperature observations for smaller radial distance.
Comment: Submitted to Geophysical Research Letters