A new, general model for radial transport of plasma, angular momentum and energy in the magnetospheres of Jupiter and Saturn
Creators: name: Devinat Marie
name: Blanc Michel
name: Nicolas, André
name: Nénon Quentin
Publisher: name: Zenodo
Year: 2022

description: The magnetospheres of giant planets are governed by the interplay of these planets’ fast rotation,<br> the solar wind and inner plasma sources. In the Saturn and Jupiter magnetospheres, plasma is mainly<br> produced by the ionization of neutral gas tori at the radial location of active moons: Io at Jupiter<br> and Enceladus at Saturn. The mechanisms by which these moon-associated plasma sources are re-<br> distributed throughout these magnetospheres involve both plasma motions and magnetic flux tube<br> exchanges. These motions are coupled to the rotation of the planets through electric current systems<br> originating in the equatorial plasma disk and closing into their upper atmosphere and ionosphere.<br> Models of the net effects of these different mechanisms on the radial transport of plasma are needed<br> to adequately reproduce the observed populations of electrons and ions in the magnetospheres of giant<br> planets and to establish the net budgets of exchange of plasma, angular momentum and energy between<br> moons, magnetospheres and their host planets. Up to now, two different types of transport models<br> have been developed. The first type (Cowley and Bunce, 2001; Cowley et al., 2005 and following<br> studies) assumes an infinitely thin plasma disk with null temperature and pressure and derives the<br> transport of angular momentum in the magnetosphere with due account of magnetosphere-ionosphere-<br> thermosphere (MIT) coupling. In the second type of model (Bagenal and Delamere, 2011; Ng et al.,<br> 2018), radial diffusion of full flux tubes with finite temperature is calculated throughout the disk,<br> taking into account hydrodynamical properties of the plasma and turbulent heating in the absence of<br> MIT coupling.<br> A self-consistent modelling of radial transport in the magnetosphere of giant planets requires the<br> unification of the two approaches into a full description of the interactions between the plasma disk<br> content, the magnetosphere and the ionosphere-thermosphere of the planet. In this communication,<br> we introduce an approach combining these two types of models to design a more general model. This<br> new type of model will describe radial transport of plasma, angular momentum and energy in the<br> Jupiter and Saturn magnetospheres taking into account both diffusive/advective plasma transport<br> and exchange of angular momentum with the planet’s upper atmosphere. It will be tested against<br> magnetosphere observations by the Juno mission at Jupiter and the Cassini mission at Saturn.
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