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Electron acceleration to non-thermal energies is known to occur in low Mach number (M<5) shocks in galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Using two-dimensional (2D)…

High Energy Astrophysical Phenomena · Physics 2014-11-26 Xinyi Guo , Lorenzo Sironi , Ramesh Narayan

We investigate the physics of particle acceleration at non-relativistic shocks exploiting two different and complementary approaches, namely a semi-analytic modeling of cosmic-ray modified shocks and large hybrid (kinetic protons/fluid…

High Energy Astrophysical Phenomena · Physics 2015-06-11 Damiano Caprioli

We use fully kinetic particle-in-cell simulations with unprecedentedly large transverse box sizes to study particle acceleration in weakly-magnetized mildly relativistic shocks traveling at a velocity $\approx 0.75c$ and a Mach number of…

High Energy Astrophysical Phenomena · Physics 2019-04-10 Patrick Crumley , Damiano Caprioli , Sera Markoff , Anatoly Spitkovsky

Particle acceleration in relativistic shocks of electron-positron plasmas with proton admixture is investigated through two-dimensional (2D) particle-in-cell (PIC) simulations. The upstream plasma, with a bulk Lorentz factor of $10$ and a…

High Energy Astrophysical Phenomena · Physics 2025-10-02 Huan Yu , Qi Xia , Jun Fang

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are…

Astrophysics · Physics 2009-11-07 K. -I. Nishikawa , P. Hardee , G. Richardson , R. Preece , H. Sol , G. J. Fishman

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are…

Astrophysics · Physics 2009-11-10 K. -I. Nishikawa , P. Hardee , G. Richardson , R. Preece , H. Sol , G. J. Fishman

A review of theoretical results on cosmic ray first-order Fermi acceleration at relativistic shock waves is presented, with recent results substantially changing the existing knowledge on these processes. In particular one can not expect…

Astrophysics · Physics 2011-11-10 M. Ostrowski

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel and other two-stream instabilities) created in collisionless shocks are responsible for particle…

Astrophysics · Physics 2015-06-24 K. -I. Nishikawa , P. Hardee , C. B. Hededal , G. Richardson , R. Preece , H. Sol , G. J. Fishman

Particle acceleration at magnetized purely perpendicular relativistic shocks in electron-ion plasmas are studied by means of two-dimensional particle-in-cell simulations. Magnetized shocks with the upstream bulk Lorentz factor $\gamma_1 \gg…

High Energy Astrophysical Phenomena · Physics 2022-01-20 Masanori Iwamoto , Takanobu Amano , Yosuke Matsumoto , Shuichi Matsukiyo , Masahiro Hoshino

Strong non-relativistic shocks are known to accelerate particles up to relativistic energies. However, for Diffusive Shock Acceleration electrons must have a highly suprathermal energy, implying a need for very efficient pre-acceleration.…

Plasma Physics · Physics 2023-10-24 Karol Fulat , Artem Bohdan , Gabriel Torralba Paz , Martin Pohl

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g.,Buneman, Weibel and other two-stream instabilities) created in collisionless shocks are responsible for particle…

Astrophysics · Physics 2009-11-10 K. -I. Nishikawa , P. Hardee , G. Richardson , R. Preece , H. Sol , G. J. Fishman

Perpendicular relativistic ($\gamma_0=10$) shocks in magnetized pair plasmas are investigated using two dimensional Particle-in-Cell simulations. A systematic survey, from unmagnetized to strongly magnetized shocks, is presented accurately…

High Energy Astrophysical Phenomena · Physics 2018-04-25 Illya Plotnikov , Anna Grassi , Mickael Grech

Plasma instabilities (e.g., Buneman, Weibel and other two-stream instabilities) excited in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a new 3-D relativistic particle-in-cell code, we…

High Energy Astrophysical Phenomena · Physics 2011-02-11 K. -I. Nishikawa , J. Niemiec , P. E. Hardee , M. Medvedev , H. Sol , Y. Mizuno , B. Zhang , M. Pohl , M. Oka , D. H. Hartmann

We study relativistic unmagnetized collisionless shocks using unprecedentedly large particle-in-cell simulations of two-dimensional pair plasma. High energy particles accelerated by the shock are found to drive magnetic field evolution on a…

Astrophysics · Physics 2009-06-23 Uri Keshet , Boaz Katz , Anatoly Spitkovsky , Eli Waxman

This proceedings paper reports on the theoretical modelling of particle acceleration in magnetised turbulent plasmas. It briefly reviews some recent findings obtained from fully kinetic numerical simulations of large-amplitude, semi to…

High Energy Astrophysical Phenomena · Physics 2025-12-18 M. Lemoine

The formation of collisionless shock fronts is an ubiquitous phenomenon in space plasma environments. In the solar wind shocks might accompany coronal mass ejections, while even more violent events, such as supernovae, produce shock fronts…

High Energy Astrophysical Phenomena · Physics 2020-03-17 Cedric Schreiner , Patrick Kilian , Felix Spanier , Patricio A. Muñoz , Jörg Büchner

We report studies on first-order Fermi acceleration in parallel modified shock waves with a large scattering center compression ratio expected from turbulence transmission models. Using a Monte Carlo technique we have modeled particle…

Astrophysics · Physics 2009-11-11 Joni J. P. Virtanen , Rami Vainio

We review recent progress on collisionless relativistic shocks. Kinetic instability theory is briefed including its predictions and limitations. The main focus is on numerical experiments in (i) pair and (ii) electron-nucleon plasmas. The…

High Energy Astrophysical Phenomena · Physics 2011-10-20 A. M. Bykov , R. A. Treumann

The course of non-thermal electron ejection in relativistic unmagnetized electron-ion shocks is investigated by performing self-consistent particle-in-cell simulations. The shocks are excited through the injection of relativistic jet into…

High Energy Astrophysical Phenomena · Physics 2016-08-24 Kazem Ardaneh , Dongsheng Cai , Ken-Ichi Nishikawa

lasma instabilities excited in collisionless shocks are responsible for particle acceleration. We have investigated the particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating…

High Energy Astrophysical Phenomena · Physics 2015-06-03 K. -I. Nishikawa , E. J. Choi , K. Min , P. Hardee , Y. Mizuno , B. Zhang , J. Niemiec , M. Medvedev , A. Nordlund , J. Fredriksen , M. Pohl , H. Sol , D. H. Hartmann , G. J. Fishman