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.