Magnetopause Dynamics at Saturn as Observed by Cassini

The occurrence and impacts of magnetopause processes at outer planets, particularly magnetic reconnection and the Kelvin‐Helmholtz instability (KHI), remains unresolved. From a list of 2,114 magnetopause crossings at Saturn spanning the full duration of the Cassini mission, magnetic field and low‐energy plasma properties are analyzed for each crossing to determine the likelihood of particular dynamical processes at Saturn's magnetopause. Using Cassini magnetic field data, crossings are categorized as (a) those with signatures of possible magnetic reconnection, (b) those near/inside a magnetopause surface wave or vortex arising from KHI, and (c) those during quiescent conditions (i.e., lacking signatures indicative of magnetic reconnection or KH waves). Of magnetopause crossings with valid intervals on both sides of the boundary, nearly half of the crossings met criteria for signatures of reconnection, with little dependence on local time or latitude of the magnetopause crossing location. Crossings identified as associated with KHI are found to more likely occur toward the dawn sector as compared to other local times, but with both flanks likely being quasi‐unstable to the instability. Magnetopause properties for crossings with available low‐energy electron data from Cassini are further explored to provide insight into the local plasma conditions that may be conducive to magnetic reconnection and/or KH waves. This investigation reveals that certain dynamics along the magnetopause of Saturn may be more prevalent than previously considered, and provides a basis for a more comprehensive understanding of magnetopause dynamics and plasma transport at the outer planets. Key Points We analyze Cassini data encompassing 2,114 magnetopause crossings to determine the occurrence of dynamical processes at Saturn's magnetopause The occurrence of reconnection is prevalent at Saturn's magnetopause and is independent of Saturn local time and latitude Observationally, we find more Kelvin‐Helmholtz signatures at dawn, but both dawn and dusk can be conducive to Kelvin‐Helmholtz instability