Exospheric heating by pickup ions at Titan

Titan has a very extensive atmosphere and exosphere which interact strongly with the corotating magnetospheric plasma. Some of the new pickup ions created in the vicinity of the exosphere will re-impact the upper atmosphere causing additional energy input. Previous investigations of the atmospheric collisional interaction of the pickup ions have generally assumed the atmosphere to be spherically symmetric. From the Voyager and Cassini observations, we know that the magnetic field configuration and plasma flow field is highly asymmetric. To study the possible spatial variation in the pickup ion influx, we have employed the plasma data of the three dimensional MHD simulation of Kopp and Ip [Kopp, A., Ip, W.-H. Asymmetric mass loading effect at Titan's ionosphere. J. Geophys. Res. 106, 8323-8332, 2001] to compute the trajectories of the pickup ions. In this work, we calculate the ion influx and energy deposit into Titan's exobase for the H ₂ ⁺ , CH ₄ ⁺ and N ₂ ⁺ pickup ions separately. The model results of four different Titan's orbital locations are also presented.