The Cassini mission yielded a treasure trove of information on Saturn's largest moon Titan. With many flybys of this complex moon Cassini revealed many aspects of Titan's upper atmosphere and interaction with Saturn's magnetosphere. In many ways Cassini revealed that this moon is unique in that it sustains a dense atmosphere and ionosphere even without the protection of an internal magnetic field. Key to the understanding of this ionosphere is understanding the ion dynamics of Titan's upper atmosphere, namely how these ions are created and lost either to the lower atmosphere where they fall and can contribute to the creation of the complex hydrocarbons seen at the surface or are carried away with Saturn's rapidly flowing magnetospheric particles. Here we present novel measurements of the velocities of many ion species in Titan's upper atmosphere. We show that multiple processes must be responsible for the acceleration of these ions as there is evidence for both mass dependent and independent acceleration. We also show that heavy, relatively complex molecular ions are accelerated and carried into the magnetospheric flow. These ions could contribute to mass loading processes and possibly additional changes in the magnetosphere when Titan resides in Saturn's magnetotail.

Here we present observations and simulations of oxygen particle bombardment into Titan’s thermosphere that represents a new class of upper atmospheric stimulus. We find that these large bursts of energetic oxygen ions contain sufficient energy to perturb Titan’s thermosphere, if the energy is applied at the right altitude. In this study we present Cassini observations during the T20 flyby of Titan in 2006 specifically from the Cassini Magnetospheric Imaging Instrument (MIMI; Krimigis et al. [2004]) and the Cassini Plasma Spectrometer (CAPS; Young et al. [2004]). We utilize simulations using the Titan-Global Ionosphere Thermosphere Model to assess the impact of energetic oxygen bursts similar to the one observed during T20 on the thermospheric structure. We find that energy deposited higher in Titan’s thermosphere has a much greater effect on the temperatures that Cassini would observe from the INMS instrument. These higher altitude energy deposition events are similar to those that occur from corotational oxygen and water group ions in Saturn’s magnetosphere. We find that the more energetic heavy ions tend to penetrate deeper into the thermosphere resulting in a much more benign heating rate and minimal temperature change, however when these events carry along lower energy thermal oxygen ions that will deposit energy at higher altitudes the temperature change can be much more substantial.

Observations of energetic charged particles associated with Io’s footprint (IFP) tail, and likely within or very near the Main Alfvén Wing, during Juno’s 12th perijove (PJ) crossing show evidence of intense proton acceleration by wave-particle heating. Measurements made by Juno/JEDI reveal proton characteristics that include pitch angle distributions concentrated along the upward loss cone, broad energy distributions that span ~50 keV to 1 MeV, highly structured temporal/spatial variations in the particle intensities, and energy fluxes as high as ~100 mW/m2. Simultaneous measurements of the plasma waves and magnetic field suggest the presence of ion cyclotron waves and transverse Alfvénic fluctuations. We interpret the proton observations as upgoing conics likely accelerated via resonant interactions with ion cyclotron waves. These observations represent the first measurements of ion conics associated with moon-magnetosphere interactions, suggesting energetic ion acceleration plays a more important role in the IFP tail region than previously considered.