Asymmetric mass loading effect at Titan's ionosphere

Authors:
  • AKAndreas Kopp
    Andreas Kopp
  • WIWing‐Huen Ip
    Wing‐Huen Ip
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Abstract
Because of the fact that Titan does not possess an intrinsic magnetic field, the corotating plasma in the Saturnian magnetosphere can interact directly with the nitrogen‐rich atmosphere of Titan. In this work we perform three‐dimensional resistive MHD simulations of the interaction between Titan and the Saturnian magnetosphere. The magnetic field of Saturn is modeled as a dipole field located at the origin of a cylindrical coordinate system. Of particular interest is the mass loading effect in the vicinity of Titan. The pickup of atmospheric ions is strongly influenced by the ionization rate and scale lengths of the system. The fact that the ion gyroradius of the system is of the order of the radius of Titan has important consequences. Ions emerging from Titan's ionosphere at the hemisphere facing toward Saturn get lost back into the ionosphere, whereas ions at the opposite hemisphere may contribute to the satellite's mass loading by enhanced atmospheric sputtering. This results in an asymmetry of the mass loading patterns between the planet‐facing hemisphere and the antiplanet hemisphere. For different mass loading ratios we investigate the effect of this asymmetry. By comparing our results with Voyager 1 measurements we conclude that a mass loading asymmetry could in principle provide an explanation of the observed deflection in the magnetic fields as well as the asymmetry of the plasma flow in the wake region.

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