A Preliminary Study of Magnetosphere‐Ionosphere‐Thermosphere Coupling at Jupiter: Juno Multi‐Instrument Measurements and Modeling Tools
Résumé
The dynamics of the Jovian magnetosphere are controlled by the interplay of the planet's fast rotation, its main iogenic plasma source and its interaction with the solar wind. Magnetosphere-Ionosphere-Thermosphere (MIT) coupling processes controlling this interplay are significantly different from their Earth and Saturn counterparts. At the ionospheric level, they can be characterized by a set of key parameters: ionospheric conductances, electric currents and fields, exchanges of particles along field lines, Joule heating and particle energy deposition. From these parameters, one can determine (a) how magnetospheric currents close into the ionosphere, and (b) the net deposition/extraction of energy into/ out of the upper atmosphere associated to MIT coupling. We present a new method combining Juno multi-instrument data (MAG, JADE, JEDI, UVS, JIRAM and Waves) and modeling tools to estimate these key parameters along Juno's trajectories. We first apply this method to two southern hemisphere main auroral oval crossings to illustrate how the coupling parameters are derived. We then present a preliminary statistical analysis of the morphology and amplitudes of these key parameters for eight among the first nine southern perijoves. We aim to extend our method to more Juno orbits to progressively build a comprehensive view of Jovian MIT coupling at the level of the main auroral oval. Plain Language Summary Jupiter's magnetosphere is dominated by the presence of a giant magnetized disk of plasma which extends from the orbit of the innermost Galilean moon Io to 50 Jovian radii and more. Plasma motion in this disk is driven mainly by the rotation of the planet and partly by its coupling to the solar wind. The upper atmosphere of the pole and the magnetized disk of plasma are coupled by a system of electric currents (from which the polar aurora is generated). As NASA's Juno spacecraft flies above the northern and southern polar regions every orbit, its different instruments measure magnetic fields, charged particles and auroral emissions. In this article we use data from this suite of instruments taken during the first nine orbits, together with adequate models, to calculate the resistivity of the auroral upper atmosphere and the characteristics of the electric currents closing through it. We also estimate the departure of plasma motions from planetary rotation and the amount of power these currents transfer between the upper atmosphere and magnetized disk. WANG ET AL.
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