Separating drivers of Saturnian magnetopause motion

Abstract

Surface waves on Saturn's magnetopause and oscillations of the magnetopause at a period associated with that of planetary rotation have previously been detected. How the amplitudes of these two key perturbations to the magnetopause position compare, however, is unclear. We construct a one-dimensional magnetopause model that considers both types of boundary dynamics and compare it to six sets of magnetopause crossings observed by the Cassini magnetometer instrument, in order to estimate and compare properties of the two phenomena. We identify their relative amplitudes to be approximately one in all cases, suggesting that magnetopause oscillations notably affect the magnetopause position, even when surface waves are present. Furthermore, using this technique, we estimate the surface wave period for crossings on 14 July 2007 as 47 min and periods for all other sets at values between 2.4 h and 4.9 h. These periods are in agreement with previous studies which employed minimum variance analysis of magnetometer data.

The magnetic structure of Saturn's magnetosheath

“…These are both inbound (bow shock to magnetopause) and outbound (magnetopause to bow shock) and exclude excursions due to global boundary oscillations or surface waves. Such excursions are generally identified as a series of crossings over a timescale much shorter than the magnetosheath traversal [ Mistry et al ., ].…”

Survey of Saturn's Magnetopause and Bow Shock Positions Over the Entire Cassini Mission: Boundary Statistical Properties and Exploration of Associated Upstream Conditions

“…The ability of the solar wind at Saturn to influence global magnetospheric dynamics is a topic of some debate. Both the magnetopause and bow shock boundaries are shown to be influenced by factors internal to the magnetosphere, such as planetary period oscillations, which can periodically change the magnetopause position by up to 2 R S (1 R S = 60,268 km; e.g., Clarke et al, 2006Clarke et al, , 2010, with other magnetopause motions suggested to be linked to plasmoid release (Zieger et al, 2010) and surface waves (Mistry et al, 2014). No strong link between magnetopause position and IMF direction has been found (Jia et al, 2012), implying that erosion due to dayside reconnection may be minimal.…”

The Near-Saturn Magnetic Field Environment

“…Since we are interested in the large-scale spatially-dependent structure of the magnetosheath, we have selected 106 complete and uninterrupted magne- These are both inbound (bow shock to magnetopause) and outbound (magnetopause to bow shock) and exclude excursions due to global boundary oscillations or surface waves. Such excursions are generally identified as a series of crossing over a timescale much shorter than the magnetosheath traversal [Mistry et al, 2014].…”