Saturn's magnetospheric dynamics

Abstract

The dynamics of Saturn's magnetosphere are driven by two major features of the system: First, the dominant source of magnetospheric plasma is the icy moon Enceladus, located deep within the magnetosphere; and second, like Jupiter, Saturn is a very fast rotator, with a rotational period of only 10.7 h. The dynamical imperative is to rid the magnetosphere of the continuously supplied plasma, and the fast rotation provides the mechanisms to do so. Thus, magnetospheric dynamics are intimately related to mass transport processes, including radial diffusion, flux tube interchange, magnetic reconnection, and plasmoid formation. We review recent progress and new questions relating to these processes at Saturn.

Cassini in situ observations of long-duration magnetic reconnection in Saturn’s magnetotail

“…The data also show evidence of magnetic reconnection over a period of 19 h revealing that reconnection can, in fact, act for prolonged intervals in a rapidly rotating magnetosphere. We show that reconnection can be a significant pathway for internal plasma loss at Saturn 6 . This counters the view of reconnection as a transient method of internal plasma loss at Saturn 5,7 .…”

“…Magnetic reconnection is also thought to be a key process involved in shedding internally produced plasma from the giant magnetospheres at Jupiter and Saturn through topological reconfiguration of the magnetic field 5,6 . The region where magnetic fields reconnect is known as the di usion region and in this letter we report on the first encounter of the Cassini spacecraft with a di usion region in Saturn's magnetotail.…”

“…Some of this plasma is lost from the system by charge exchange; the remaining plasma is transported radially outward. The radial transport is driven by the centrifugal interchange instability, which is analogous to the Rayleigh-Taylor instability with gravity replaced by the centrifugal force associated with the rapid rotation of the magnetosphere 6 . Magnetic reconnection is a process involving topological rearrangement of the magnetic field.…”

The Near-Saturn Magnetic Field Environment

“…This leads to a RayleighTaylor instability setting up where the cold and dense inner plasma is interchanged with hot and tenuous from the outer magnetosphere. This process is driven by the outward centrifugal force associated with Saturn's rapid rotation rate [Thomsen et al, 2013]. The standoff distance (i.e.…”

Saturn Plasma Sources and Associated Transport Processes

“…Jackman et al, 2008b; and the global magnetosphere (in terms of changing plasma flows, flux closure, mass removal) (McAndrews et al, 2009;Jia et al, 2012a;Thomsen et al, 2013) have been explored by a number of authors since the observation of the first three cases with magnetic field (Jackman et al, 2007) and plasma data . We refer the reader to these papers and to the reviews of Thomsen (2013) and Jackman (2014) for further comprehensive description of Saturn's magnetotail dynamics. For a comprehensive review of the dynamics of Saturn's magnetotail, compared and contrasted with Mercury, Earth and Jupiter, we refer to Jackman et al (2014a).…”