Injection to Rapid Diffusive Shock Acceleration at Perpendicular Shocks in Partially Ionized Plasmas

Abstract

We present a three-dimensional hybrid simulation of a collisionless perpendicular shock in a partially ionized plasma for the first time. In this simulation, the shock velocity and the upstream ionization fraction are v sh ≈ 1333 km/s and f i ∼ 0.5, that are typical values for isolated young supernova remnants in the interstellar medium. We confirm previous two-dimensional simulation results that downstream hydrogen atoms leak into the upstream region, they are accelerated by the pickup process in the upstream region, and large magnetic field fluctuations are generated both in the upstream and downstream regions. In addition, we find that the magnetic field fluctuations have three-dimensional structures and the leaking hydrogen atoms are injected to the diffusive shock acceleration at the perpendicular shock after the pickup process. The observed diffusive shock acceleration can be interpreted as the shock drift acceleration with scattering. Particles are accelerated to v ∼ 100 v sh ∼ 0.3 c within ∼ 100 gyroperiods in this simulation. The acceleration time scale is faster than that of the diffusive shock acceleration in parallel shocks. Our simulation results suggest that supernova remnants can accelerate cosmic rays to 10 15.5 eV (the knee) during the Sedov phase.

Particle acceleration model for the broad-band baseline spectrum of the Crab nebula

“…We have shown that the synchrotron spectrum is produced by electrons in the GeV -TeV range orbiting around a large-scale magnetic field with strength B0 = 140 µG. The value of B0 probes the region behind and close to the shock where cooling length-scale of TeV electrons is small; the field B0 might be the result of local amplification due to the inhomogeneities of the pulsar wind advected through the shock (see Mizuno et al (2014) for relativistic and Fraschetti (2013) for non-relativistic flows) and the brid simulations for high-Mach number supernova remnant shocks travelling, e.g., in partially ionized fluid (Ohira 2016).…”

PIC simulation methods for cosmic radiation and plasma instabilities

“…For a shock speed below 3000 km/s, about 10% of the upstream neutral particles leak back into the upstream region [240]. Ohira [241] conducted 3D hybrid simulations and demonstrated that the pick-up ions drive fast-mode turbulence that upon contact with the shock induce vorticity and drive further magnetic-field amplification akin that described by Giacalone & Jokipii [100]. Particles can be accelerated to high energy by shock-drift acceleration in the motional electric field in the upstream region.…”

Shock Drift Acceleration of Ions in an Interplanetary Shock Observed by MMS

“…Both SDA and DSA are invoked in more general astrophysical cases as well, particularly to explain observations of cosmic rays and supernova remnants (Biermann et al 2018;Caprioli & Spitkovsky 2014;Gargaté & Spitkovsky 2012;Ohira 2016;Park et al 2015;Zank et al 2015). Lario et al (2019) have described IP shock observations where enhancements in ions less than 10 keV appeared close to the shock.…”