The magnetosheaths of the outer planets

Abstract

This paper provides a review of past work on the magnetosheaths of the outer planets and also provides the most complete look to date at the plasma parameters in these magnetosheaths. We find that proton distributions in the magnetosheaths of Jupiter, Saturn, and Neptune (but not Uranus) are well represented by two Maxwellians with the same velocity but different temperatures. The hot proton component comprises about 40% of the total density and has a temperature about six times that of the cold protons. The Jovian magnetosheath shows significant motion, with sunward flow not uncommon when the magnetosheath region moves outwards, probably due to changes in solar wind pressure. Gas dynamic models of the boundaries show that the magnetospheres of Jupiter and Saturn are flattened at the poles. Deviations from the predictions of gas dynamics are observed, both because of time-dependent effects and systematic effects such as encounters with the plasma depletion layer and plasma mantle, both of which are MHD effects. Mirror mode waves are ubiquitous in the magnetosheaths, but other waves and oscillations are also observed, including one so far unique to Uranus which may occur downstream of parallel shocks.