dHybridR: a Hybrid--Particle-in-Cell Code Including Relativistic Ion Dynamics

TL;DR

dHybridR is a novel hybrid particle-in-cell simulation code that models relativistic ion dynamics in non-relativistic plasmas, enabling studies of cosmic-ray effects on astrophysical shock phenomena with new self-consistent results.

Contribution

The paper introduces dHybridR, the first hybrid PIC code incorporating relativistic ion dynamics, and demonstrates its capabilities through simulations of cosmic-ray acceleration and shock phenomena.

Findings

Relativistic ions are accelerated at non-relativistic shocks with a power-law distribution.

CRs develop a broken power law in energy, consistent with diffusive shock acceleration theory.

The code successfully simulates real-time evolution of shocks relevant to astrophysical observations.

Abstract

We present the first plasma simulations obtained with the code dHybridR, a hybrid particle-in-cell code with fluid electrons and both thermal and energetic ions that retain relativistic dynamics. dHybridR is constructed to study astrophysical and space-physics problems where a few energetic non-thermal particles (i.e., cosmic rays, CRs) affect the overall dynamics of a non-relativistic plasma, such as CR-driven instabilities, collisionless shocks, magnetic reconnection, turbulence, etc.In this method paper we provide some applications to linear (resonant/non-resonant CR streaming instability) and strongly non-linear (parallel shocks) problems that show the capabilities of the code. In particular, we provide the first self-consistent hybrid runs that show the acceleration of relativistic ions at non-relativistic shocks; CRs develop a power-law in momentum, which translates to a broken power law in energy that exhibits a steepening around the ion rest mass, as predicted by the theory of diffusive shock acceleration. We present examples of 2D dHybridR runs relevant for fast shocks in radio supernovae, whose evolution can be followed in real time, and 3D runs of low-Mach-number heliospheric shocks, which can be compared with in-situ spacecraft observations.