Turbulent Heating in Jupiter's Middle Magnetosphere from Juno Data

The ion temperature in Jupiter’s middle magnetosphere (about 10 to 35 Jupiter radii) has been known to increase as a function of radial distance from the planet faster than adiabatic cooling. This suggests that there is a non-adiabatic heating process occurring in this region. Efforts have been made to explain this heating using different turbulent heating models and data from previous science missions to Jupiter [Saur, Astrophys. J., 602, L137 (2004); Ng et al. J. Geophys. Res., 123, 6611 (2018); Geophys. Res. Lett., 49, e2021GL096662 (2022)]. Using Juno spacecraft magnetometer data and particle data based on a forward fitting model, the turbulent heating rate density is obtained based on observed energy spectra assuming Alfvén/kinetic Alfvén waves turbulence models. The average turbulent heating rate density is found to be generally less than what was obtained using Galileo data, by about half an order of magnitude. On the other hand, ion temperatures from Juno data are found to be about an order of magnitude higher than previously reported. Because of these two new observations, the Ng et al. 2018 advection turbulent heating model is not sufficient to account for the ≈ 108K temperatures seen in the fits. Therefore, new heating models are needed to explain the new observations.