Can we observe the effects of gradient drift on convecting plasma using ENA imagery?

Kinrade, Joe and Badman, Sarah and Paranicas, Chris and Rhodes, Will (2025) Can we observe the effects of gradient drift on convecting plasma using ENA imagery? In: Autumn MIST 2025, 2025-11-28 - 2025-11-28, Geological Society of London, Burlington House, Piccadilly.

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Abstract

The Cassini mission to Saturn captured wide-area imagery of energetic neutral atom (ENA) emissions that emanate from regions of ongoing charge exchange in the magnetosphere. Images typically show diffuse emission enhancements that rotate around the planet following reconnection activity in the magnetotail, as energetic plasma interacts with Saturn’s extended neutral cloud. These ENA features often have counterpart signatures in both ultraviolet auroral and kilometric radio emissions, and can persist for several days after strong injection events. Using a set of re-calibrated and re-projected imagery, we superpose the under-studied high energy (90-230 keV) Oxygen bands of Cassini's Ion-Neutral Camera (INCA) with the lower energy Hydrogen bands in order to show the extent that energy-dependent gradient drifts can be resolved. Superposition of the imagery in this way requires a homogeneous set of projections that has not existed until recently. Most morphological studies use lower energy 24-55 keV Hydrogen images that - due to backscatter effects in the instrument - provide better spatial resolution and count rates. We therefore focus on the most intense events observed by the Cassini INCA, and track the morphology and spatial extent of the ENA emission using image segmentation at each INCA energy range.