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Title: Electron Heating in 2D Particle-in-cell Simulations of Quasi-perpendicular Low-beta Shocks

We measure the thermal electron energization in 1D and 2D particle-in-cell simulations of quasi-perpendicular, low-beta (βp= 0.25) collisionless ion–electron shocks with mass ratiomi/me= 200, fast Mach numberMms=1–4, and upstream magnetic field angleθBn= 55°–85° from the shock normalnˆ. It is known that shock electron heating is described by an ambipolar,B-parallel electric potential jump, Δϕ, that scales roughly linearly with the electron temperature jump. Our simulations haveΔϕ/(0.5miush2)0.1–0.2 in units of the pre-shock ions’ bulk kinetic energy, in agreement with prior measurements and simulations. Different ways to measureϕ, including the use of de Hoffmann–Teller frame fields, agree to tens-of-percent accuracy. Neglecting off-diagonal electron pressure tensor terms can lead to a systematic underestimate ofϕin our low-βpshocks. We further focus on twoθBn= 65° shocks: aMs=4(MA=1.8) case with a long, 30diprecursor of whistler waves alongnˆ, and aMs=7(MA=3.2) case with a shorter, 5diprecursor of whistlers oblique to bothnˆandB;diis the ion skin depth. Within the precursors,ϕhas a secular rise toward the shock along multiple whistler wavelengths and also has localized spikes within magnetic troughs. In a 1D simulation of theMs=4,θBn= 65° case,ϕshows a weak dependence on the electron plasma-to-cyclotron frequency ratioωpece, andϕdecreases by a factor of 2 asmi/meis raised to the true proton–electron value of 1836.

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DOI PREFIX: 10.3847
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Journal Name:
The Astrophysical Journal
Medium: X Size: Article No. 37
["Article No. 37"]
Sponsoring Org:
National Science Foundation
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