Magnetopause Compressibility at Saturn with Internal Drivers

Abstract

We use magnetopause crossings of the Cassini spacecraft to study the response of Saturn's magnetosphere to changes in external and internal drivers. We explain how solar wind pressure can be corrected to account for the local variability in internal plasma particle pressure. The physics‐based method is applied to perform the most robust estimation of magnetopause compressibility at Saturn to date, using 7 years' worth of magnetometer data from the Cassini mission and accounting for variable internal drivers—particle pressure and azimuthal ring current. The concept of magnetopause compressibility is generalized to quantitatively account for its detailed variation with respect to the position of the magnetopause. An analytical fit is provided to map the compressibility index to values of the stand‐off distance. In particular, the procedure shows that the Kronian system appears to behave similarly to that of Jupiter when expanded outwards and more like the Earth's magnetopause when compressed.