Real-time 3-D hybrid simulation of Titan's plasma interaction during a solar wind excursion

Abstract

Abstract. The plasma environment of Saturn's largest satellite Titan is known to be highly variable. Since Titan's orbit is located within the outer magnetosphere of Saturn, the moon can leave the region dominated by the magnetic field of its parent body in times of high solar wind dynamic pressure and interact with the thermalized magnetosheath plasma or even with the unshocked solar wind. By applying a threedimensional hybrid simulation code (kinetic description of ions, fluid electrons), we study in real-time the transition that Titan's plasma environment undergoes when the moon leaves Saturn's magnetosphere and enters the supermagnetosonic solar wind. In the simulation, the transition between both plasma regimes is mimicked by a reversal of the magnetic field direction as well as a change in the composition and temperature of the impinging plasma flow. When the satellite enters the solar wind, the magnetic draping pattern in its vicinity is reconfigured due to reconnection, with the characteristic time scale of this process being determined by the convection of the field lines in the undisturbed plasma flow at the flanks of the interaction region. The build-up of a bow shock ahead of Titan takes place on a typical time scale of a few minutes as well. We also analyze the erosion of the newly formed shock front upstream of Titan that commences when the moon re-enters the submagnetosonic plasma regime of Saturn's magnetosphere. Although the model presented here is far from governing the full complexity of Titan's plasma interaction during a solar wind excursion, the simulation provides important insights into general plasma-physical processes associated with such a disruptive change of the upstream flow conditions. Keywords. Magnetospheric physics (Magnetosphere interactions with satellites and rings; Magnetosphere-ionosphere interactions) -Space plasma physics (Kinetic and MHD theory)

Magnetic tension in the tails of Titan, Venus and comet Halley

“…In principle, the Hall effect may also lead to the rotation of the magnetic field vector around the tail axis (as shown in Fig. 3), but this rotation was not observed in kinetic (Kallio et al, 2004) and hybrid (Simon et al, 2006, 2007a,b, 2008, Simon, 2009Modolo et al, 2007) simulations which automatically include the Hall effect; (c) relative role of the effects of electromagnetic induction due to temporal variations of the magnetic field (∂B/∂t) in the magnetospheric plasma flow (Podgorny et al, 1982;Saur et al, 2010). These effects might exceed the effects of Lorentz induction (v  B) in the Titan magnetosphere, since the flow velocity is subsonic and the variations of the Kronian magnetic field in the corotating flow are significant.…”

“…Backes, 2004;Ma et al, 2006), hybrid (e.g. Simon et al, 2006, 2007a,b, 2008, Simon, 2009Modolo et al, 2007), kinetic (Kallio et al, 2004) -succeeded to reproduce day side magnetic field line draping similar to that shown in Fig. 2, asymmetry of the magnetic field strength and deflection of the tail from the corotation flow direction toward Saturn (Kallio et al, 2004;Ma et al, 2006) and away from Saturn (Simon et al, 2007a,b;Modolo et al, 2007).…”