Modeling Io's and Europa's Plasma Interaction with the Jovian Magnetosphere: Influence of Global Atmospheric Asymmetries and Plumes

• Main Author: Blöcker, Aljona
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2017
• Subjects: ddc:530; ddc:550; South Pole; South pole
• Online Access: https://kups.ub.uni-koeln.de/7741/; https://kups.ub.uni-koeln.de/7741/1/Diss_bearb.pdf

We apply a three-dimensional (3D) magnetohydrodynamic (MHD) model to study the influence of inhomogeneities in Europa’s and Io’s atmospheres, as, for example, water vapor plumes and volcanic plumes, on the plasma interaction with the Jovian magnetosphere. The ideal MHD equations have been extended in order to account for the effects of the moons’ atmospheres and plumes on the plasma interaction. We have included collisions between ions and neutrals, plasma production and loss due to electron impact ionization and dissociative recombination. Moreover, electromagnetic induction in a subsurface water ocean was also considered by the model in modeling of Europa’s plasma interaction. In addition to the MHD model we apply an analytic model based on the model of Saur et al. (2007) to understand the role of steep gradients and discontinuities in Europa’s interaction. We find that Europa’s global atmosphere weakens the effect of the hemisphere coupling and generates steep gradients in the magnetic field. Volcanic eruptions on Io and water vapor plumes on Europa locally enhance the neutral density of the atmosphere and thus modify the plasma interaction. We show that an inhomogeneity near the north or south pole affects the plasma interaction in a way that a pronounced north-south asymmetry is generated. We find that an Alfvén winglet develops within the main Alfvén wing on that side where the inhomogeneity is located. Since Europa’s atmosphere is much thinner (by a factor of 100 compared to Io’s atmosphere) we show that dense atmospheric inhomogeneities affect the Alfvénic far-field much stronger compared to Io. At Europa the plasma velocity experiences a decrease up to 95% of the upstream velocity in the Alfvén winglet and a decrease up to 60% of the upstream velocity in the ambient Alfvén wing. Whereas at Io the plasma flow is decelerated by up to 93% in the Alfvén winglet and by more than 80% in the ambient Alfvén wing. Simultaneously, the Alfvén waves perturb also the magnetic field in the Alfvénic far-field so that ...