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Finding the injection threshold for diffusive shock acceleration (DSA) of electrons in collisionless shocks has been a longstanding unsolved problem. Using first-principles kinetic simulations, we identify the conditions for electron…

High Energy Astrophysical Phenomena · Physics 2025-06-12 Siddhartha Gupta , Damiano Caprioli , Anatoly Spitkovsky

There are two distinct breaks in the cosmic ray (CR) spectrum: the so-called "knee" around $3 \times 10^{15}$ eV and the so-called "ankle" around $10^{18}$ eV. Diffusive shock acceleration (DSA) at supernova remnant (SNR) shock fronts is…

High Energy Astrophysical Phenomena · Physics 2017-01-25 Chad Bustard , Ellen G. Zweibel , Cory Cotter

Although many of the observed properties of giant radio relics detected in the outskirts of galaxy clusters can be explained by relativistic electrons accelerated at merger-driven shocks, significant puzzles remain. In the case of the…

High Energy Astrophysical Phenomena · Physics 2017-06-06 Hyesung Kang , Dongsu Ryu , T. W. Jones

Galactic cosmic rays are widely believed to be accelerated in expanding shock waves initiated by supernova explosions. The theory of diffusive shock acceleration of cosmic rays is now well established, but two fundamental questions remain…

Astrophysics · Physics 2008-07-25 Vincent Tatischeff

We have performed 2D hybrid simulations of non-relativistic collisionless shocks in the presence of pre-existing energetic particles ("seeds"); such a study applies, for instance, to the re-acceleration of Galactic cosmic rays (CRs) in…

High Energy Astrophysical Phenomena · Physics 2018-07-18 Damiano Caprioli , Horace Zhang , Anatoly Spitkovsky

We calculate the energy spectra of cosmic ray (CR) protons and electrons at a plane shock with quasi-parallel magnetic fields, using time-dependent, diffusive shock acceleration (DSA) simulations, including energy losses via synchrotron…

High Energy Astrophysical Phenomena · Physics 2017-01-18 Hyesung Kang

It is well accepted today that diffusive acceleration in shocks results to the cosmic ray spectrum formation. This is in principle true for non-relativistic shocks, since there is a detailed theory covering a large range of their properties…

Astrophysics · Physics 2007-08-13 A. Meli , A. Mastichiadis

We present a model for the non-thermal emission from a colliding-wind binary. Relativistic protons and electrons are assumed to be accelerated through diffusive shock acceleration (DSA) at the global shocks bounding the wind-wind collision…

High Energy Astrophysical Phenomena · Physics 2020-04-29 J. M. Pittard , G. S. Vila , G. E. Romero

Context. Radio relics in galaxy clusters are known to be good laboratories for verification of the applicability of the diffusive shock acceleration (DSA) model in its canonical version. The need for such verification stems from the…

High Energy Astrophysical Phenomena · Physics 2021-03-17 Grazyna Siemieniec-Ozieblo , Mariia Bilinska

We develop a self-consistent nonlinear extension of diffusive shock acceleration that incorporates cosmic ray (CR) backreaction on the shock precursor together with a physically motivated upstream-escape mechanism that produces an…

High Energy Astrophysical Phenomena · Physics 2026-02-17 Han-Xiang Hu , Xing-Jian Lv , Xiao-Jun Bi , Tian-Lu Chen , Kun Fang , Peng-Fei Yin

We introduce a Monte Carlo model of nonlinear diffusive shock acceleration allowing for the generation of large-amplitude magnetic turbulence. The model is the first to include strong wave generation, efficient particle acceleration to…

Astrophysics · Physics 2008-11-26 Andrey Vladimirov , Donald C. Ellison , Andrei Bykov

Diffusive shock acceleration (DSA) is a prominent mechanism for energizing charged particles up to very large rigidities at astrophysical collisionless shocks. In addition to ions and electrons, it has been proposed that interstellar dust…

High Energy Astrophysical Phenomena · Physics 2024-10-31 P. Cristofari , V. Tatischeff , M. Chabot

We discuss new methods to integrate the cosmic ray (CR) evolution equations coupled to magneto-hydrodynamics (MHD) on an unstructured moving mesh, as realised in the massively parallel AREPO code for cosmological simulations. We account for…

Astrophysics of Galaxies · Physics 2017-01-11 C. Pfrommer , R. Pakmor , K. Schaal , C. M. Simpson , V. Springel

Supernova remnants (SNRs) are believed to accelerate particles up to high energies through the mechanism of diffusive shock acceleration (DSA). Except for direct plasma simulations, all modeling efforts must rely on a given form of the…

High Energy Astrophysical Phenomena · Physics 2015-06-22 Gilles Ferrand , Rebecca J. Danos , Andreas Shalchi , Samar Safi-Harb , Paul Edmon , Peter Mendygral

Galactic cosmic rays (CRs) are accelerated by astrophysical shocks, primarily supernova remnants (SNRs), via diffusive shock acceleration (DSA), an efficient mechanism that predicts power-law energy distributions of CRs. However,…

High Energy Astrophysical Phenomena · Physics 2021-09-24 Rebecca Diesing , Damiano Caprioli

We investigate the diffusive shock acceleration in the presence of the non-resonant streaming instability introduced by Bell (2004). The numerical MHD simulations of the magnetic field amplification combined with the analytical treatment of…

Astrophysics · Physics 2009-11-13 V. N. Zirakashvili , V. S. Ptuskin

One of the key questions to understanding the efficiency of diffusive shock acceleration of the cosmic rays (CRs) is the injection process from thermal particles. A self-consistent injection model based on the interactions of the…

Astrophysics · Physics 2007-05-23 U. D. J. Gieseler , T. W. Jones , Hyesung Kang

We examine the cosmic-ray protons (CRp) accelerated at collisionless shocks in galaxy clusters using cosmological structure formation simulations. We find that in the intracluster medium (ICM) within the virial radius of simulated clusters,…

High Energy Astrophysical Phenomena · Physics 2020-04-08 Ji-Hoon Ha , Dongsu Ryu , Hyesung Kang

We propose semi-analytic models for the electron momentum distribution in weak shocks that accounts for both in situ acceleration and re-acceleration through diffusive shock acceleration (DSA). In the former case, a small fraction of…

High Energy Astrophysical Phenomena · Physics 2020-11-25 Hyesung Kang

The mechanism of diffusive Fermi acceleration at collisionless plasma shock waves is widely invoked in astrophysics to explain the appearance of non-thermal particle populations in a variety of environments, including sites of cosmic ray…

Astrophysics · Physics 2007-05-23 Matthew G. Baring