Journal of Geophysical Research: Space Physics

Cover image for Vol. 122 Issue 7

Impact Factor: 3.426

ISI Journal Citation Reports © Ranking: 2014: 19/175 (Geosciences Multidisciplinary)

Online ISSN: 2169-9402

Associated Title(s): Journal of Geophysical Research

Plasma injection events in Saturn's magnetosphere


Periodic radio emissions, including the strong radio emissions known as the Saturn kilometric radio (SKR) emissions, originate from the northern and southern polar regions and are observed throughout Saturn’s magnetosphere. Scientists have been studying these phenomena but have not been able to pin down the physical mechanism linking periodicities between the inner and outer magnetospheres.

One proposed mechanism is a process known as the centrifugal interchange instability, which occurs in rapidly rotating magnetospheres such as Saturn’s. In this process, the cold, dense plasma moves radially outward from the planet and hotter, less dense plasma is injected inward.

Small-scale and large-scale inward flowing injections of hot plasma have been observed in Saturn’s magnetosphere. Adding to the understanding of these processes, Kennelly et al. focused on young small-scale injection events observed using the Radio and Plasma Wave Science instrument on the Cassini spacecraft between July 2004 and December 2011. They analyzed the regions where these injection events are most likely to occur and concluded that these inward flowing injection events are strongly ordered and that this ordering depends on the Saturnian season. Their ordering is well correlated with the SKR originating from the hemisphere experiencing winter (pointing away from the Sun). The study suggests that injection events could play a role in communicating the periodicities observed in the inner and outer magnetosphere and provides insight into the interchange instability that could be of interest to others studying the magnetospheres of outer planets.

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