The statistical morphology of Saturn's equatorial energetic neutral atom emission

Kinrade, Joe and Bader, Alexander and Badman, Sarah and Paranicas, C. and Mitchell, Donald. G. and Constable, DA and Arridge, Chris and Cowley, S.W.H. and Provan, G. (2021) The statistical morphology of Saturn's equatorial energetic neutral atom emission. Geophysical Research Letters, 48 (11): e2020GL091. ISSN 0094-8276

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Abstract

Saturn's magnetosphere is an efficient emitter of energetic neutral atoms (ENAs), created through charge exchange of energetic ions with the extended neutral cloud originating from the icy moon Enceladus. We present an analysis using the complete image set captured by Cassini’s Ion Neutral Camera (INCA) to characterise Saturn’s average ENA morphology. Concentric tori are formed around the planet by oxygen and hydrogen ENAs, with intensity peaks between 7-10 Rs radial distance, with a ~1-2 Rs dayside offset. Nightside intensity is brighter than the dayside, likely the result of enhancements following large-scale plasma injections from the magnetotail, and influence of the noon-midnight electric field. Global intensity is clearly modulated with the near-planetary rotation period. This Cassini-era profile of Saturn's ENA emission advances our understanding of how volcanic moons can influence plasma dynamics in giant magnetospheres and is timely ahead of the planned JUICE mission, which carries the first dedicated ENA detector to Jupiter.