Dynamic escape of H from Titan as consequence of sputtering induced heating

In previous investigations on nonthermal escape processes on Saturns large moon Titan, the authors (Lammer and Bauer) showed that dissociation of +2 ions and impact dissociation of N2 by magnetospheric electron precipitation lead to nitrogen escape rates much lower than atmospheric sputtering processes via energetic magnetospheric N+ ions and protons or solar wind protons. Energetic processes like Titans plasma interaction with Saturns magnetosphere, however, can affect Titans upper atmosphere. It is shown that the bulk of the energetic N+ ions is deposited below the exobase, a region where no temperature determinations by occultation methods exist. This present study takes into account all sources of energy fluxes, heat conduction and other thermal transport processes and estimated horizontal wind velocities of about 100–300 m/s. We found that the energy deposition of magnetospheric N+ ions is responsible for heating effects in Titans atmosphere, corresponding to a rise in the temperature up to 30 K above the presently assumed. Thus, sputtering-induced heating would lead to higher Jeans escape rates for neutral hydrogen atoms and may represent an additional source for populating and heating Saturns neutral hydrogen torus. Sputtering by magnetospheric and solar wind protons will yield, however, only negligible small heating effects of Titans thermosphere.