The role of ionospheric O+ outflow in the generation of earthward propagating plasmoids

Abstract

Earthward propagating plasmoids in the Earth's magnetotail have been observed by satellites. Using a multifluid global magnetosphere simulation, earthward propagating plasmoids are reproduced when ionospheric O+ outflow is included in the global simulation. Controlled simulations show that without ionospheric outflow, the plasmoids generated in the magnetotail during a substorm-steady magnetospheric convection cycle only propagate tailward. With ionospheric outflow, earthward plasmoids can be induced through the modification of magnetotail reconnection at multiple X lines. When multiple X lines form in the magnetotail, plasmoids may be trapped between multiple reconnection sites. When magnetic reconnection rate is reduced at the near-Earth X line by the presence of ionospheric O+, the earthward exhaust flow of reconnection occurring at the midtail X line forces the plasmoid to propagate earthward. The propagation speed and spatial size of the simulated earthward plasmoid are consistent with observations from the Cluster satellites.