Magnetic reconnection and kinetic waves generated in the Earth's quasi-parallel bow shock

Abstract

Magnetic reconnection in quasi-parallel shocks, relevant to the Earth's bow shock, is studied by means of two-dimensional full particle-incell simulations. As the Alfv enic Mach number increases, the propagation direction of the waves excited in the transition region changes, and the shock becomes more turbulent with more reconnection sites. In the higher Mach number shock, abundant electron-only reconnection sites are generated with scales on the order of the ion skin depth or less. Non-reconnecting current sheets can also generate electron jets and energy dissipation can occur there as well. However, non-reconnecting current sheets with the magnetic field reversal typically show a smaller energy dissipation rate than reconnecting current sheets. In the shock transition region, two types of waves are responsible for driving reconnection: one has a wavelength around three ion skin depths (d i ), and the other has a wavelength less than 1 d i . Electron and ion distribution functions show that in regions where the former type of waves is excited, there are two ion beams and a single-peaked electron distribution. In contrast, in regions where the latter type of waves is excited, there are multiple electron and ion beams. The waves propagating obliquely to the magnetic field bend the magnetic field lines, and magnetic reconnection occurs where oppositely directed field lines come into contact.

Identification of Active Magnetic Reconnection Using Magnetic Flux Transport in Plasma Turbulence

“…This category has U ψ reversals, but no plasma outflow jet reversal. Electron-only reconnection with only one jet is also reported in simulations of shock-driven turbulence (Bessho et al 2020).…”

Solar Wind Discontinuity Transformation at the Bow Shock

“…The bow shock crossing may alter the RD properties (e.g., increase the current density or form a plasma pressure gradient across the discontinuity) and make RDs unstable to magnetic reconnection. This would explain a large number of observational reports about magnetic reconnection and charged particle acceleration in the magnetosheath (Retinò et al 2007;Phan et al 2018;Gingell et al 2020;Wang et al 2020;Bessho et al 2020). We emphasise the role of accelerated particles in the RD-shock interaction and the current density amplification.…”

“…Note that magnetic field fluctuations and waves in the magnetosheath significantly perturb B l and cause oscillations of j m . These effects lead to strong intermittent local currents, which in turn may make the discontinuity unstable to magnetic reconnection (e.g., Gingell et al 2020;Wang et al 2020;Bessho et al 2020).…”

Solitary Magnetic Structures at Quasi‐Parallel Collisionless Shocks: Formation

“…The |B| and N variations are positively correlated for both ULF waves and isolated SLAMS. Most SLAMS in the shown interval contain a sharp bipolar B z , which are likely to be further compressed into thin current sheets that are conducive to magnetic reconnection (Bessho et al, 2019(Bessho et al, , 2020Gingell et al, 2019Gingell et al, , 2020Wang et al, 2019Wang et al, , 2020a.…”