Problem description:

Icy moons, embedded in the magnetoplasma of a planetary magnetosphere will display various phenomena. First of all, the surface of the moon will be bombarded with the co-rotating plasma that overtakes the moon and sputtering processes will take place. Atoms and ions will be ?kicked off? the surface. The ions will connect to the magnetic field, mass loading the field. The neutrals will create an exosphere, and will be ionized through impact ionization or charge exchange. This process creates a so-called pick-up current which acts to slow down the upstream plasma flow. This current is closed through field aligned currents, which in their turn create the so-called Alfvén wings [Neubauer 1998, 1999]. For a review on the topic see Kivelson et al. [2004].

Near Europa, in Jupiter?s magnetosphere Galileo observations have shown that there is, indeed, sputtering and ion pick-up present around the moon [Volwerk et al., 2001] and that Alfvén wings are created [Khurana and Kivelson, 1999, Volwerk et al., 2007]. The slowing down of the plasma has been observed [Kivelson et al., 2009] near Europa and ion pick-up on the upstream side of the moon has indeed been found [Volwerk et al., 2010].

Enceladus, in Saturn?s magnetosphere, is a geologically active moon, in the sense that it gets stretched and compressed by tidal forces, whilst orbiting Saturn. This heats up the inner regions of the moon and on the South Pole this results in a reservoir of liquid water. This water is released into the Kronian magnetosphere through a series of vents [Hansen et al., 2006; Porco et al., 2006]. These water plumes drastically influence the interaction of the magnetoplasma with the moon; it creates a strong asymmetry [Saur et al., 2007]. The sputtering off the moon, mass loading the system [Pontius and Hill, 2009] and these water plumes create a torus at Enceladus? orbit [Johnson et al., 2006].

• Hansen, C. J., et al., Enceladus? water vapor plume, Science, 311, 1422?1425, 2006.

• Johnson, R. E.; Smith, H. T.; Tucker, O. J.; Liu, M.; Burger, M. H.; Sittler, E. C.; Tokar, R. L., The Enceladus and OH Tori at Saturn, Astrophys. J., 644, L137-L139, 2006.

• K. K. Khurana and M.G. Kivelson, Inner Jovian magnetosphere: mass-loading near Europa, EOS, 80, F875, 1999.

• M. G. Kivelson, F. Bagenal, W. S. Kurth, F. M. Neubauer, C. Paranicas and J. Saur, Magnetospheric interactions with satellites, in: Jupiter: The Planet, Satellites and Magnetosphere, eds. F. Bagenal, T. E. Dowling and W. B. McKinnon, Cambridge University Press, Cambridge , UK, 513 - 536, 2004.

• M. G. Kivelson, K. K. Khurana and M. Volwerk, Europa's interaction with the Jovian magnetosphere, in: Europa, eds. R. T. Pappalardo, W. B. McKinnon and K. K. Khurana, University of Arizona Press, Tucson, USA, 545-570, 2009.

• F. M. Neubauer, The sub-Alfvénic interaction of the Galilean satellites with the Jovian magnetosphere, J. Geophys. Res.,  103, 19834-19866, 1998.

• F. M. Neubauer, Alfvén wings and electromagnetic induction in the interiors: Europa and Callisto, J. Geophys. Res., 104, 28671-28684, 1999.

• D. H. Pontius and T. W. Hill, Plasma mass loading from the extended neutral gas torus of Enceladus as inferred from the observed plasma corotation lag, Geophys, Res. Lett., 36, L23103, doi: 10.1029/2009GL041030, 2009.

• Porco, C., et al., Cassini observes the active south pole of Enceladus, Science, 311, 1393? 1401, 2006.

• Saur, J., F. M. Neubauer, and N. Schilling, Hemisphere coupling in Enceladus? asymmetric plasma interaction, J. Geophys. Res., 112, A11209, doi: 10.1029/2007JA012479, 2007.

• M. Volwerk, M. G. Kivelson and K. K. Khurana, Wave activity in Europa's wake: Implications for ion pick-up, J. Geophys. Res., 106, 26033-26048, 2001.

• M. Volwerk, K. Khurana and M. Kivelson, Europa's Alfvén wing; shrinkage and displacement influenced by an induced magnetic field, Ann. Geophys., 25, 905-914, 2007.

• M. Volwerk, M. G. Kivelson and K. K. Khurana, Ion pick-up near the icy Galilean satellites, submitted, 2010.