Reconnection at Saturns Dayside Magnetopause: Cusp and Flux Rope observations by Cassini

Magnetic reconnection at a dayside magnetopause couples a magnetosphere to the solar wind. This process drives the dynamics at Earth and Mercurys magnetospheres. The conditions at Saturns magnetopause are more likely to suppress magnetic reconnection from occurring. Therefore, it is important to understand reconnection at Saturns magnetosphere to determine how important this process is in driving its dynamics under these conditions. We present an overview analysis of cusp plasma observations at the Saturnian magnetosphere from the Cassini spacecraft era. The cusp is an important magnetospheric region to investigate because it funnels shocked solar wind plasma into the magnetosphere. The cusps are also important in the transfer of energy and momentum from the solar wind to the magnetosphere. Evidence for bursty and more continuous reconnection signatures have been observed at different cusp events at Saturn. We find that cusp plasma is injected under a variety of upstream solar wind conditions and that reconnection takes place at a variety of magnetopause locations for single cusp events. We also present recent discoveries of flux transfer events (FTEs) at Saturns dayside magnetopause. These flux rope magnetic structures are generated by multiple x-line reconnection. The observed FTEs have diameters close to or above the ion inertial length, considerably lower than typical FTEs found at Earth. The FTEs magnetic flux contents are 4461 kWb, considerably smaller (<0.1%) than the average flux opened during magnetopause compression events at Saturn. This is in contrast to Earth and Mercury where FTEs contribute significantly to magnetospheric flux transfer. FTEs therefore represent a negligible proportion of the amount of open magnetic flux transferred at Saturn. Due to diamagnetic suppression of reconnection at Saturn's magnetopause, we suggest that the typical size of FTEs at Saturn is most likely very small, and that there may be more ion-scale FTEs present in the Cassini magnetometer data that have not been identified due to their brief and unremarkable magnetic signatures.