Two-dimensional modeling of longitudinal modulations in the Io plasma torus

Abstract:

The longitudinal modulation in the Io plasma torus has been an open question for decades. A major clue to the cause of the torus modulation was provided by the discovery of the key modulation of the hot electron (i.e. ∼ 100s eV) population, at both the System III (magnetic rotation period) and System IV (∼ 3% longer than System III) period [Steffl et al., 2008]. However, very little progress has been made in explaining the origin of these hot electron modulations. Using a new two-dimensional (coupled radial and azimuthal dimensions) physical chemistry model for the plasma torus, we present sensitivity studies of torus properties (e.g., composition, density, and temperature) to: a) variations in System III and IV hot electron populations, b) specified radial profiles of subcorotation, and c) subcorotation determined by local mass loading rates and ionospheric Pedersen conductance. We also explore a possible feedback between hot electron production and local radial transport rates following the suggestion of Hess et al., [2011] regarding the origin of System IV hot electrons.

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