Abstract
Abstract. We use a global hybrid-Vlasov simulation for the magnetosphere, Vlasiator, to investigate magnetosheath high-speed jets. Unlike many other hybrid-kinetic simulations, Vlasiator includes an unscaled geomagnetic dipole, indicating that the simulation spatial and temporal dimensions can be given in SI units without scaling. Thus, for the first time, this allows investigating the magnetosheath jet properties and comparing them directly with the observed jets within the Earth's magnetosheath. In the run shown in this paper, the interplanetary magnetic field (IMF) cone angle is 30∘, and a foreshock develops upstream of the quasi-parallel magnetosheath. We visually detect a structure with high dynamic pressure propagating from the bow shock through the magnetosheath. The structure is confirmed as a jet using three different criteria, which have been adopted in previous observational studies. We compare these criteria against the simulation results. We find that the magnetosheath jet is an elongated structure extending earthward from the bow shock by ∼2.6 RE, while its size perpendicular to the direction of propagation is ∼0.5 RE. We also investigate the jet evolution and find that the jet originates due to the interaction of the bow shock with a high-dynamic-pressure structure that reproduces observational features associated with a short, large-amplitude magnetic structure (SLAMS). The simulation shows that magnetosheath jets can develop also under steady IMF, as inferred by observational studies. To our knowledge, this paper therefore shows the first global kinetic simulation of a magnetosheath jet, which is in accordance with three observational jet criteria and is caused by a SLAMS advecting towards the bow shock.
Highlights
Earth’s magnetosphere is surrounded by the magnetosheath, which consists of shocked and turbulent plasma of solar wind origin
It shows a snapshot of a movie S1, depicting the dynamic pressure at time t = 305.5 s from the beginning of the run
As we show that the dynamic pressure rapidly decreases as a function of distance from the bow shock, to observe jets closer to the magnetopause it may be better to choose the Archer and Horbury (2013) criterion
Summary
Earth’s magnetosphere is surrounded by the magnetosheath, which consists of shocked and turbulent plasma of solar wind origin. The sunward boundary of this region is the bow shock through which the solar wind plasma flows into the magnetosheath. The bow shock and magnetosheath plasma properties relative to those in the upstream pristine solar wind depend broadly. At the quasi-parallel shock, part of the solar wind particles reflect back towards the Sun (Schwartz et al, 1983; Meziane et al, 2004), causing instabilities and waves upstream, and forming a so-called foreshock. The region downstream from the quasi-parallel shock is called the quasi-parallel magnetosheath, where the plasma properties are highly turbulent (e.g., Fuselier et al, 1991; Gutynska et al, 2012). The magnetosheath downstream from the quasi-perpendicular bow shock hosts a variety of locally generated waves, e.g., mirror mode waves (Soucek et al, 2015; Hoilijoki et al, 2016)
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