Mapping transition region flows to the ionosphere in a hybrid-Vlasov simulation

The formation of plasma flow channels in the magnetotail has recently been investigated using several modeling and observations approaches. The aim of this study is to investigate the formation and evolution of such plasma flow channels by utilizing the global magnetospheric hybrid-Vlasov model Vlasiator, now featuring an ionospheric boundary model. In a recent simulation run we observe the formation of large-scale flow bursts that enter the inner magnetosphere, driving azimuthally spread vortex flows. These vortices are magnetically connected to the ionosphere via field-aligned currents. Thus we investigate ionosphere-magnetosphere coupling using the Vlasiator simulation.

We find that the flow channels form as a result of magnetic reconnection in the tail, in combination with the ballooning/interchange instability. The event shows signatures of both of these interconnected phenomena. The scale of the flow channels in the magnetotail is about 3.5 R_E (Earth radii) in the azimuthal direction, and about 2000 km in the ionosphere. The duration of the event from the formation to the dissipation of the vortex flows is around 300 seconds. We study the relevant processes related to the ballooning/interchange instability, including e.g., flux tube entropy, and the effects of the plasma flow on the magnetic field in the magnetotail.