Current events at Saturn: ring–planet electromagnetic coupling

Agiwal, O., Cao, H., Hsu, H.-W., Moore, L., Sulaiman, A. H., O'Donoghue, J. ORCID: https://orcid.org/0000-0002-4218-1191 and Dougherty, M. K. (2024) Current events at Saturn: ring–planet electromagnetic coupling. The Planetary Science Journal, 5 (6). 134. ISSN 2632-3338 doi: 10.3847/PSJ/ad4343

Abstract/Summary

This study presents a synthesized analysis of in situ and ground-based observations to investigate electromagnetic coupling between Saturn and its rings. During the Cassini Grand Finale, the magnetometer detected gradients in the azimuthal magnetic field Bf connected to Saturn’s B-ring on 17 out of 21 orbits. The Bf gradients indicate that field-aligned currents are flowing into Saturn’s B-ring at ∼1.55–1.67 RS in the ring plane, preferentially in the southern hemisphere. On average, these currents are magnetically conjugate with ground-based observations of nonsolar enhancements in H+3 emissions from Saturn’s ionosphere and detected contemporaneously with ringsourced, planetward electron beams and field-aligned charged dust grain inflow from the C- and B-rings into Saturn’s atmosphere. Collectively, these observations align with Voyager-era predictions of a phenomenon known as “ring rain,” where charged ring material generated inward of a nominal “critical radius” is drawn into Saturn’s upper atmosphere along the magnetic field. However, we show that the B-ring currents are not likely to be a direct signature of infalling field-aligned ring grains. Instead, we propose that the ring rain generation mechanism naturally results in a sharp gradient in the ionospheric Pedersen conductance at the ∼1.57–1.67 RS boundary, which, combined with a v × B electric field in the ring ionosphere, could drive the observed B-ring currents. The Pedersen conductance in the high-conductance region of the southern ring ionosphere is constrained to ∼0.07–2 S and is observed to vary within this range on week-long timescales.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/120070
Identification Number/DOI	10.3847/PSJ/ad4343
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	IOP Publishing
Download/View statistics	View download statistics for this item