Kinetic Simulation of Nonrelativistic Perpendicular Shocks of Young Supernova Remnants. IV. Electron Heating

Abstract

High-Mach-number collisionless shocks are found in planetary systems and supernova remnants (SNRs). Electrons are heated at these shocks to temperatures well above the Rankine-Hugoniot prediction. However, the processes responsible for causing the electron heating are still not well understood. We use a set of large-scale particle-in-cell simulations of nonrelativistic shocks in the high-Mach-number regime to clarify the electron heating processes. The physical behavior of these shocks is defined by ion reflection at the shock ramp. Further interactions between the reflected ions and the upstream plasma excites electrostatic Buneman and two-stream ion-ion Weibel instabilities. Electrons are heated via shock surfing acceleration, the shock potential, magnetic reconnection, stochastic Fermi scattering, and shock compression. The main contributor is the shock potential. The magnetic field lines become tangled due to the Weibel instability, which allows for parallel electron heating by the shock potential. The constrained model of electron heating predicts an ion-to-electron temperature ratio within observed values at SNR shocks and in Saturn's bow shock.Unified Astronomy Thesaurus concepts: Shocks (2086); Plasma astrophysics (1261); Supernova remnants (1667); Interstellar medium (847)

Magnetic Field Amplification by the Weibel Instability at Planetary and Astrophysical Shocks with High Mach Number

“…The downstream region is at x − x sh < −5λ si . This structure is representative for all runs and for the high-M A regime in general [30,31,36,[41][42][43][44]. Earlier linear analysis [30] and its adaptation to our study [43] both indicate that high-M A shocks are Weibel-instability mediated.…”

“…Electron preacceleration [36,43] and heating [44] strongly depend on the structure and strength of the magnetic field. At quasiperpendicular shocks, where stochastic shock drift acceleration (SSDA) is expected to operate [29,47], a strong magnetic field generated by the Weibel instability limits the mean free path and increases the cyclotron frequency of electrons, and so the cutoff energy of SSDA may depend on M A .…”

Statistical analysis of correlations in the x-ray induced Coulomb explosion of iodopyridine

“…The downstream is a region behind the overshoot, at − sh −5 si . The described structure is representative for all runs and in general for high-Mach-number shocks [15][16][17][18][19][20][21].…”

Saturation of the asymmetric current filamentation instability under conditions relevant to relativistic shock precursors

“…As such, it controls the production of high-energy particles and radiation in such environments, whether in the near [39] or the remote Universe [26]. Because of their paramount consequences, those "Weibelmediated" collisionless shocks have inspired a large body of literature, both in the subrelativistic [40][41][42][43][44][45][46][47][48][49] and relativistic regimes [36,[50][51][52][53][54][55][56][57][58][59][60][61][62][63]. Long-standing issues, with obvious phenomenological implications in the aforementioned domains of research, are the level of saturation of the CFI [12,[64][65][66][67][68][69][70][71][72] and the long-term evolution of the self-generated magnetic turbulence [46,[73][74][75][76][77][78].…”