Kinetic simulations of turbulent magnetic-field growth by streaming cosmic rays

Abstract

Efficient acceleration of cosmic rays (via the mechanism of diffusive shock acceleration) requires turbulent, amplified magnetic fields in the shock's upstream region. We present results of multidimensional particle-in-cell simulations aimed at observing the magnetic field amplification that is expected to arise from the cosmic-ray current ahead of the shock, and the impact on the properties of the upstream interstellar medium. We find that the initial structure and peak strength of the amplified field is somewhat sensitive to the choice of parameters, but that the field growth saturates in a similar manner in all cases: the back-reaction on the cosmic rays leads to modification of their rest-frame distribution and also a net transfer of momentum to the interstellar medium, substantially weakening their relative drift while also implying the development of a modified shock. The upstream medium becomes turbulent, with significant spatial fluctuations in density and velocity, the latter in particular leading to moderate upstream heating; such fluctuations will also have a strong influence on the shock structure.

8 pages, 6 figures, accepted by ApJ

References in corpus (6)

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• Modeling Bell's Non-resonant Cosmic Ray Instability
• Turbulence Dissipation and Particle Injection in Non-Linear Diffusive Shock Acceleration with Magnetic Field Amplification
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• Magnetic Amplification by Magnetized Cosmic Rays in SNR Shocks
• A filamentation instability for streaming cosmic-rays
• Magnetic Field Amplification and Saturation in Turbulence Behind a Relativistic Shock
• Particle Spectra from Acceleration at Forward and Reverse Shocks of Young Type Ia Supernova Remnants
• PIC Simulation Methods for Cosmic Radiation and Plasma Instabilities
• On the Growth and Saturation of the Gyroresonant Streaming Instabilities
• Nonrelativistic parallel shocks in unmagnetized and weakly magnetized plasmas
• The nonlinear saturation of the non-resonant kinetically driven streaming instability
• Amplification of perpendicular and parallel magnetic fields by cosmic ray currents
• Reacceleration of electrons in supernova remnants
• Electron Heating, Magnetic Field Amplification, and Cosmic Ray Precursor Length at Supernova Remnant Shocks
• Aperiodic magnetic turbulence produced by relativistic ion beams
• Spatio-temporal evolution of the nonresonant instability in shock precursors of young supernova remnants
• Could Cosmic Rays Affect Instabilities in the Transition Layer of Nonrelativistic Collisionless Shocks?
• Magnetic and density spikes in cosmic ray shock precursors
• Macroscopic magnetization of primordial plasma by virial shocks
• Time-dependent treatment of cosmic-ray spectral steepening due to turbulence driving