Titan's magnetic wake: Atmospheric or magnetospheric interaction

Abstract

We compare the magnetic field topology in the Titan wake to an idealized picture of magnetic field lines draping about a conductive nonmagnetic obstacle. It is shown that in the inner part of the wake the magnetic field picture differs significantly from that expected for an idealized draping: The transverse magnetic field component rotates by 90° as compared with the direction of the upstream transverse magnetic field. Another difference is the existence of a deep magnetic field minima separating the inner and outer parts of the wake. Transverse magnetic field rotation can be explained neither by temporal changes in the upstream magnetic field nor by reconnection processes in the wake. We find that this behavior of the transverse magnetic field can be explained at least qualitatively if one assumes the existence of a small intrinsic magnetic field of Titan. An effective magnetic dipole of 1021 G cm3 can account for the observed topology of the Titan magnetic wake. The origin of this field may be related to a residual magnetization of Titan's crust or to induction in a conducting ionosphere of the satellite. We present results of MHD simulations which support the above theoretical conclusion.