Cassini Data Analysis and Drift-Physics Modeling of Energetic Plasma Injections in Saturn's Magnetosphere

The Cassini spacecraft collected energetic plasma (3-220 keV) and magnetic field data from the CHarge Energy Mass Spectrometer (CHEMS) and magnetometer (MAG) instruments, including hundreds of observations of small-scale injection events of energetic plasma into the inner magnetosphere. The differing density regions of plasma, along with the rapid rotation of Saturn, drive an aspect of plasma transport most similar to a Rayleigh-Taylor instability. CHEMS can be used to identify high-energy plasma injection events, which appear as a sudden increase in ion flux intensity. We used a model which inputs the identified injection events along with corotation estimates, observed flux data, pitch angles, and gradient curvature drift estimations to evolve these injections over time around the equatorial plane of Saturn. The evolved events were then compared against Cassini observations if their predicted path intersected the Cassini spacecraft again within 0.25 R _s (Saturn radii). Our analysis of these events determined that out of the 816 events, only 243 original injections would further intersect the Cassini's trajectory again. By comparing the model's predictions with CHEMS spectrogram data, we found that a majority (181 injections) were determined to be "channel-like", or radially extended, because they aligned with an observed dispersed ion signature, while 62 did not match a channel-like morphology. Most of the events required slight adjustments to the model's drift speeds which improved our fit to the modeled particles on the spectrogram. The model was set to assume the Wilson et al. 2017 calculated 50th percentile co-rotation velocity, and while this worked for 77 events, a best-fit corotation rate was on average 9% faster than our nominal setting. Additionally, we found that decreasing the drift of the magnetic gradient-curvature drift term by 9% from our nominal setting created a best fit to the energy-dependent dispersion.