External triggering of plasmoid development at Saturn

Abstract

The Cassini spacecraft has encountered multiple plasmoids in Saturn's magnetotail thought to be produced by tail reconnection. However, single spacecraft measurements make it difficult to determine plasmoid size, where they form, the composition, and the geometry of the plasma sheet when plasmoids are produced. This paper examines these issues using 3D multifluid simulations of the Kronian magnetosphere. Plasmoids may develop in multiple sectors, form at different distances from the planet, and grow to sizes large relative to the system (∼25 R_S), with varying widths and lengths. These plasmoids are composed primarily of water group ions and move downtail with speeds of ∼250 km/s (the local Alfvén speed). The plasma sheet is hinged upward both prior to and following plasmoid formation. Plasmoids can be externally triggered by both flips in the orientation of the interplanetary magnetic field (IMF) as well as a pulse in the solar wind dynamic pressure.