Modeling Jupiter's magnetosphere: Influence of the internal sources

摘要

We introduce a new model to study Jupiter's magnetosphere and how it interacts with the solar wind. We first derive a set of one-fluid MHD equations to consistently include the ion-neutral collisions in Jupiter's ionosphere and the mass loading in the Io torus. The mass loading and the subsequent radial mass transport in Jupiter's magnetosphere leads to a deviation from full corotation of the magnetospheric plasma. Ion-neutral collisions in Jupiter's ionosphere and subsequent transport of angular momentum out into the magnetosphere acts to spin up the magnetosphere's plasma. Our model explicitly includes mass loading in the Io plasma torus and an inner boundary region, which represents the effects of Jupiter's ionosphere. We present the results of five model runs where different mass loading rates and ionospheric conductances are used. For these model runs, we consider an antiparallel interplanetary magnetic field and a strong solar wind dynamic pressure, resulting in a compressed magnetosphere. The results are compared with analytical models, in situ measurements, and remote-sensing observations. Our azimuthal velocity profiles and the position of the corotation breakdown are in quantitative agreement with theoretical predictions by Hill (1979, 2001) and Saur et al., (2004a), and Voyager observations. The total current flowing into and out of the ionosphere is 48.7MA, which is in agreement with estimates from measurements and analytical models. Using the field aligned electric current j(vertical bar) to determine the position of the aurorae, we find that our main auroral oval is associated, as expected, with the position of the corotation breakdown (between 20.6R(J) and 30.1R(J) for the different model runs). The discontinuity in the main oval observed by Radioti et al. (2008) is also present in our results, where it is caused by an asymmetry in the pressure distribution, due to the interaction between the rotating plasma and the magnetopause.