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Current Events at Saturn: Electromagnetic Erosion of the Rings

Presentation #110.05 in the session Many Planets, More Rings Posters (Poster + Lightning Talk)

Published onOct 23, 2023
Current Events at Saturn: Electromagnetic Erosion of the Rings

The Cassini magnetometer detected a signature that is magnetically connected to Saturn’s B-ring during the Grand Finale, which remains unresolved to date. We analyse this signature and show that it is indeed the first magnetic field detection of ring-planet electromagnetic coupling at Saturn. The field-aligned currents derived from the magnetic field measurements are on-average consistent with electrons flowing from the rings into Saturn’s mid-latitude ionosphere, which was also observed by the Cassini RPWS instrument during the Grand Finale. The field-aligned currents magnetically map to ~1.62 Saturn radii in the ring plane, which is a well modelled region of instability in Saturn’s rings where ‘ring rain’ is expected to originate. This detection is in agreement with literature from the Voyager era, which hypothesised that the density structure of the main rings may be a result of on-going electromagnetic erosion. While the signature is detected in both hemispheres, the signal is stronger and observed more frequently in the southern hemisphere, which is consistent with model predictions of ring-planet electromagnetic coupling that consider the northward offset of Saturn’s internal magnetic field. Finally, the magnetic field measurements are used to empirically constrain the electrical conductance of the ‘ring-atmosphere’ to < 0.02 S above the outer B-ring.

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