Kronian Magnetospheric Reconnection Statistics Across Cassini’s Lifetime

Garton, T. M., Jackman, C. M. and Smith, Andy (2021) Kronian Magnetospheric Reconnection Statistics Across Cassini’s Lifetime. Journal of Geophysical Research: Space Physics, 126 (8). e2021JA029361. ISSN 2169-9380

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Abstract

Magnetic reconnection is a fundamental physical process in planetary magnetospheres, in which plasma can be exchanged between the solar wind and a planetary magnetosphere, and material can be disconnected and ultimately lost from a magnetosphere. Magnetic reconnection in a planetary magnetotail can result in the release of plasmoids downtail and dipolarizations planetward of an x-line. The signatures of these products include characteristic deflections in the north-south component of the magnetic field which can be detected by in-situ spacecraft. These signatures have been identified by eye, semi-automated algorithms, and recently machine learning (ML) methods. Here, we apply statistical analysis to the most thorough catalog of Kronian magnetospheric reconnection signatures created through ML methods to improve understanding of magnetospheric evolution. This research concludes that no quasi-steady position of the magnetotail x-line exists within 70 (Formula presented.). This research introduces prediction equations to estimate the distribution of duration of plasmoid passage over the spacecraft ((Formula presented.), bin width = 1 min) and north-south field deflection ((Formula presented.), bin width = 0.25 nT) expected to be identified by an orbiting spacecraft across a year of observations. Furthermore, this research finds a local time asymmetry for reconnection identifications, with a preference for dusk-side over dawn-side. This may indicate a preference for Vasyliunas style reconnection over Dungey style for Saturn. Finally, through these distributions, the reconnection rate of Saturn’s magnetotail can be estimated as 3.22 reconnection events per day, with a resulting maximum mass loss from plasmoids of 44.87 kg (Formula presented.) on average, which is comparable with the magnetospheric mass loading from Enceladus (8–250 kg (Formula presented.)).

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