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A durable electron density peak near the inner edge of the Io torus

Presentation #324.02 in the session Giant Planet Magnetospheres, Ionospheres and Aurorae (Poster + Lightning Talk)

Published onOct 23, 2023
A durable electron density peak near the inner edge of the Io torus

The Juno Waves instrument has made several passes through the inner edge of the Io torus near M=5 at low to mid-latitudes that reveal a local peak in the electron density. This peak appeared in Voyager observations at low latitudes and Galileo passed through this region late in its mission during the A34 orbit. In this paper we use cutoffs and resonances observed in the plasma wave spectrum to determine the electron density in the inner Io torus and track this relative maximum in density to magnetic latitudes as high as 32°. Dictated by the nature of Juno’s near-polar orbit and precession of its line of apsides, Juno did not begin to explore the low-latitude inner torus until late in the prime mission. On thirteen of the perijoves (PJ) between PJ33 and PJ51, a local maximum in the electron density was observed on M-shells inside of ~5. The density maximum ranged between 2 and 30 cm-3 for most of the passes, but one outlier peak was at 65 cm-3. The peak density decreases with increasing centrifugal latitude as one might expect in rapidly rotating, heavily mass-loaded Jovian magnetosphere. The peaks occur at M = 4.90 ± 0.1 and extend for 0.1 ± 0.06 M. This translates to features with durations of about 5 minutes in the Juno observations. The outlier occurred during PJ46. It was extremely narrow, lasting about 30 seconds and having a full width at half maximum of about 0.01 M. It was also the only event to clearly occur outside of M= 5, at M=5.1.

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