Electron Pre-acceleration at Nonrelativistic High-Mach-number Perpendicular Shocks

Journal Article · Wed Sep 20 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA872A· OSTI ID:22875766

Bohdan, Artem; Niemiec, Jacek; Kobzar, Oleh ^[1]; Pohl, Martin ^[2]

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1. Instytut Fizyki Ja̧drowej PAN, ul. Radzikowskiego 152, 31-342 Kraków (Poland)
2. Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam (Germany)

We perform particle-in-cell simulations of perpendicular nonrelativistic collisionless shocks to study electron heating and pre-acceleration for parameters that permit the extrapolation to the conditions at young supernova remnants. Our high-resolution large-scale numerical experiments sample a representative portion of the shock surface and demonstrate that the efficiency of electron injection is strongly modulated with the phase of the shock reformation. For plasmas with low and moderate temperature (plasma beta β{sub p}=5⋅10{sup −4} and β{sub p}=0.5), we explore the nonlinear shock structure and electron pre-acceleration for various orientations of the large-scale magnetic field with respect to the simulation plane, while keeping it at 90° to the shock normal. Ion reflection off of the shock leads to the formation of magnetic filaments in the shock ramp, resulting from Weibel-type instabilities, and electrostatic Buneman modes in the shock foot. In all of the cases under study, the latter provides first-stage electron energization through the shock-surfing acceleration mechanism. The subsequent energization strongly depends on the field orientation and proceeds through adiabatic or second-order Fermi acceleration processes for configurations with the out-of-plane and in-plane field components, respectively. For strictly out-of-plane field, the fraction of suprathermal electrons is much higher than for other configurations, because only in this case are the Buneman modes fully captured by the 2D simulation grid. Shocks in plasma with moderate β{sub p} provide more efficient pre-acceleration. The relevance of our results to the physics of fully 3D systems is discussed.

• OSTI ID: 22875766
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 847; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CAPTURE
COMPUTERIZED SIMULATION
ELECTRON BEAM INJECTION
ELECTRONS
ELECTROSTATICS
EXTRAPOLATION
HEATING
INSTABILITY
MACH NUMBER
MAGNETIC FIELDS
NONLINEAR PROBLEMS
ORIENTATION
PLASMA
REFLECTION
RESOLUTION
SUPERNOVA REMNANTS