A new form of Saturn's magnetopause using a dynamic pressure balance model, based on in situ, multi-instrument Cassini measurements

摘要

The shape and location of a planetary magnetopause can be determined by balancing the solar wind dynamic pressure with the magnetic and thermal pressures found inside the boundary. Previous studies have found the kronian magnetosphere to show rigidity (like that of Earth) as well as compressibility (like that of Jupiter) in terms of its dynamics. In this paper we expand on previous work and present a new model of Saturn's magnetopause. Using a Newtonian form of the pressure balance equation, we estimate the solar wind dynamic pressure at each magnetopause crossing by the Cassini spacecraft between Saturn Orbit Insertion in June 2004 and January 2006. We build on previous findings by including an improved estimate for the solar wind thermal pressure and include low-energy particle pressures from the Cassini plasma spectrometer's electron spectrometer and high-energy particle pressures from the Cassini magnetospheric imaging instrument. Our improved model has a size-pressure dependence described by a power law DP−1/5.0 ± 0.8. This exponent is consistent with that derived from numerical magnetohydrodynamic simulations.