Magnetosheath jet properties and evolution as determined by a global hybrid-Vlasov simulation

Abstract

Abstract. We use a global hybrid-Vlasov simulation for the magnetosphere, Vlasiator, to investigate magnetosheath highspeed jets. Unlike many other hybrid-kinetic simulations, Vlasiator includes an unscaled geomagnetic dipole, indicating that the simulation spatial and temporal dimensions can be given 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 5 of the quasi-parallel magnetosheath. We visually detect a structure with high dynamic pressure propagating from the bow shock towards the magnetopause. 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 of the bow shock by ∼2.3 R E , while its size perpendicular to the direction of propagation is ∼0.5 R E . We also investigate the jet evolution, and find that the jet originates due to the interaction of the 10 foreshock Ultra Low Frequency (ULF) waves with the bow shock surface. The simulation shows that magnetosheath jets can develop also under steady IMF, as inferred by observational studies.

Properties of Magnetic Reconnection and FTEs on the Dayside Magnetopause With and Without Positive IMF Bx Component During Southward IMF

“…However, the large extent of the magnetosheath in the simulation does not affect the local physics that occur at the bow shock, in the magnetosheath, and at the magnetopause. Vlasiator simulations have been found to reproduce observed features of the foreshock velocity distributions and waves (Kempf et al, ; Palmroth et al, ; Pfau‐Kempf et al, ; Turc et al, ), foreshock transients (Blanco‐Cano et al, ), magnetosheath mirror mode waves (Hoilijoki et al, ) and high‐speed jets (Palmroth et al, ), and reconnection rates at the dayside magnetopause (Hoilijoki et al, ).…”

Classifying Magnetosheath Jets using MMS - Statistical Properties

“…Regarding jets, it has been suggested that jets associated with SLAMS can have a relative increase of density and magnetic field strength whereas the ones associated with purely bow shock ripple mechanism may be mainly velocity driven (Karlsson et al, 2015). Furthermore, there have been recent simulations supporting the creation of a SLAMS-like subset of jets (Palmroth et al, 2018).…”

Classifying Magnetosheath Jets Using MMS: Statistical Properties

“…Regarding jets, it has been suggested that jets associated with SLAMS can have a relative increase of density and magnetic field strength whereas the ones associated with purely bow shock ripple mechanism may be mainly velocity driven (Karlsson et al, 2015). Furthermore, there have been recent simulations supporting the generation of a SLAMS‐like subset of jets (Palmroth et al, 2018).…”