Abstract. Fast plasma flows produced as outflow jets from reconnection sites or X lines
are a key feature of the dynamics in the Earth's magnetosphere. We have used
a polar plane simulation of the hybrid-Vlasov model Vlasiator, driven by
steady southward interplanetary magnetic field and fast solar wind, to study
fast plasma sheet ion flows and related magnetic field structures in the
Earth's magnetotail. In the simulation, lobe reconnection starts to produce
fast flows after the increasing pressure in the lobes has caused the plasma
sheet to thin sufficiently. The characteristics of the earthward and tailward
fast flows and embedded magnetic field structures produced by multi-point
tail reconnection are in general agreement with spacecraft measurements
reported in the literature. The structuring of the flows is caused by
internal processes: interactions between major X points determine the
earthward or tailward direction of the flow, while interactions between minor
X points, associated with leading edges of magnetic islands carried by the
flow, induce local minima and maxima in the flow speed. Earthward moving
flows are stopped and diverted duskward in an oscillatory (bouncing) manner
at the transition region between tail-like and dipolar magnetic fields.
Increasing and decreasing dynamic pressure of the flows causes the transition
region to shift earthward and tailward, respectively. The leading edge of the
train of earthward flow bursts is associated with an earthward propagating
dipolarization front, while the leading edge of the train of tailward flow
bursts is associated with a tailward propagating plasmoid. The impact of the
dipolarization front with the dipole field causes magnetic field variations
in the Pi2 range. Major X points can move either earthward or tailward,
although tailward motion is more common. They are generally not advected by
the ambient flow. Instead, their velocity is better described by local
parameters, such that an X point moves in the direction of increasing
reconnection electric field strength. Our results indicate that ion kinetics
might be sufficient to describe the behavior of plasma sheet bulk ion flows
produced by tail reconnection in global near-Earth simulations. Keywords. Magnetospheric physics (magnetospheric configuration and dynamics; plasma sheet) – space plasma physics (numerical simulation studies)