Titan is the largest moon of the Saturnian system. Its radius is about 2575km. This moon is covered by a thick atmosphere which is dominated by nitrogen similar to the Earth atmosphere. The similarity to the Earth atmosphere makes Titan a subject of special interest. In high altitudes the atmosphere becomes ionized and it forms the ionosphere. Titan does not possess an intrinsic magnetic field. Hence, from the point of plasmaphysical view it has some analogy to Mars and Venus. However, in general Titan is not exposed to the solar wind as it moves inside Saturn's magnetosphere. The type of interaction is therefore very different to the types of Mars or Venus, respectively. The relative speed of the magnetospheric plasma flowing against Titan is subsonic, submagnetosonic and superalfvénic. The characteristic spatial scale of the interaction region is in the order of the gyroradii of the involved ions. This makes the hybrid code the method of choice for modeling the situation.
The figure shows a typical plasma environment of Titan which has been simulated using the hybrid code. The density of the plasma component coming from the left is displayed. This component represents Saturn's magnetospheric plasma. No bow shock is formed although the magnetospheric plasma is compressed by a factor of two in its maximum. No magnetospheric plasma penetrates close to Titan. Obviously it is shielded effectively by Titan's ionospheric nitrogen plasma. The magnetospheric Saturnian plasma and the ionospheric plasma of Titan are not really merged. In part a boundary layer with the character of an Ion Composition Boundary is formed. In the tail region (blue) only a small amount of magnetospheric plasma is found [Figure: Sven Simon, TU Braunschweig, 2007].
The simulated parameters are directly comparable with observed data. During the Cassini mission Titan was passed several times by the spacecraft and its plasma environment was analyzed. The combination of simulation and observation allows for the analysis of the complexity of Titan's interaction with Saturn's magnetosphere and for tracing it back to basic plasmaphysical processes.
For a more detailed description of our Titan studies as well as for several animations, the reader is referred to the German version of this page.
References
Simon, S., A. Boesswetter, T. Bagdonat, U. Motschmann, K.H. Glassmeier, Plasma environment of Titan: a 3d hybrid simulation study, Annales Geophys., 24, 1113-1135, 2006.
Simon, S., A. Boesswetter, T. Bagdonat, U. Motschmann, Physics of the ion composition boundary: a comparative 3-D hybrid simulation study of Mars and Titan, Ann. Geophys., 25, 99-115, 2007
Simon, S., A. Boesswetter, T. Bagdonat, U. Motschmann, J. Schuele, Three-dimensional multispecies hybrid simulation of Titan's highly variable plasma environment, Ann. Geophys., 25, 117-144, 2007.
Simon, S., G. Kleindienst, A. Boesswetter, T. Bagdonat, U. Motschmann, K.H. Glassmeier, J. Schuele, M.K. Dougherty, Titan's magnetic field signature during the Cassini T9 flyby - magnetometer data versus 3D multispecies hybrid simulations, Geophys. Res. Lett., 34, L24508, doi:10.1029/2007GL029967, 2007
S. Simon,U. Motschmann, G. Kleindienst, K.-H. Glassmeier, C. Bertucci, M. K. Dougherty, Titan's magnetic field signature during the Cassini T34 flyby: Comparison between hybrid simulations and MAG data (2008), Geophysical Research Letters, 35, L04107, Link.
Simon, S., Motschmann, U., and Glassmeier, K.-H.: Influence of non-stationary electromagnetic field conditions on ion pick-up at Titan: 3-D multispecies hybrid simulations (2008), Ann. Geophys., 26, 599-617, Link.
Simon, S., Motschmann, U., Kleindienst, G., Saur, J., Bertucci, C. L., Dougherty, M. K., Arridge, C. S., and Coates, A. J.: Titan's plasma environment during a magnetosheath excursion: Real-time scenarios for Cassini's T32 flyby from a hybrid simulation (2009), Ann. Geophys., 27, 669-685, Link.
Sven Simon, Uwe Motschmann, Titan's induced magnetosphere under non-ideal upstream conditions: 3D multi-species hybrid simulations (2009), Planetary and Space Science, Volume 57, Issues 14-15, Pages 2001-2015, Link.
Joachim Müller, Sven Simon, Uwe Motschmann, Karl-Heinz Glassmeier, Joachim Saur, Josef Schüle, Gavin J. Pringle (2010), Magnetic field fossilization and tail reconfiguration in Titan's plasma environment during a magnetopause passage: 3D adaptive hybrid code simulations, Planetary and Space Science, Volume 58, Issue 12, Pages 1526-1546, Link.