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A study of collisionless external shocks in gamma-ray bursts is presented. The shock structure, electromagnetic fields, and process of electron acceleration are assessed by performing a self-consistent 3D particle-in-cell (PIC) simulation.…

High Energy Astrophysical Phenomena · Physics 2015-09-30 Kazem Ardaneh , Dongsheng Cai , Ken-Ichi Nishikawa , Bertrand Lembége

The collisionless plasmas in space and astrophysical environments are intrinsically multiscale in nature, behaving as conducting fluids at macroscales and kinetically at microscales comparable to ion- and/or electron-gyroradii. A…

Collisionless shocks tend to send charged particles into the upstream, driving electric currents through the plasma. Using kinetic particle-in-cell simulations, we investigate how the background thermal plasma neutralizes such currents in…

High Energy Astrophysical Phenomena · Physics 2023-12-22 Siddhartha Gupta , Damiano Caprioli , Anatoly Spitkovsky

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

We investigate the long-time evolution of magnetic fields generated by the two-stream instability at ultra- and sub-relativistic astrophysical collisionless shocks. Based on 3D PIC simulation results, we introduce a 2D toy model of…

We present two-dimensional hybrid kinetic/magnetohydrodynamic simulations of planned laser-ablation experiments in the Large Plasma Device (LAPD). Our results, based on parameters which have been validated in previous experiments, show that…

Plasma Physics · Physics 2016-12-21 M. S. Weidl , D. Winske , F. Jenko , C. Niemann

We study the long term evolution of magnetic fields generated by a collisionless relativistic $e^+e^-$ shock which is initially unmagnetized. Our 2D particle-in-cell numerical simulations show that downstream of such a Weibel-mediated…

Astrophysics · Physics 2009-11-13 P. Chang , A. Spitkovsky , J. Arons

Nonrelativistic electrostatic unmagnetized shocks are frequently observed in laboratory plasmas and they are likely to exist in astrophysical plasmas. Their maximum speed, expressed in units of the ion acoustic speed far upstream of the…

Plasma Physics · Physics 2015-06-15 ME Dieckmann , H Ahmed , G Sarri , D Doria , I Kourakis , L Romagnani , M Pohl , M Borghesi

A full particle simulation study is carried out for studying microinstabilities generated at the shock front of perpendicular collisionless shocks. The structure and dynamics of shock waves are determined by Alfven Mach number and plasma…

Plasma Physics · Physics 2015-06-04 Takayuki Umeda , Yoshitaka Kidani , Shuichi Matsukiyo , Ryo Yamazaki

Large-amplitude electrostatic fluctuations are routinely observed by spacecraft upon traversal of collisionless shocks in the heliosphere. Kinetic simulations of shocks have struggled to reproduce the amplitude of such fluctuations,…

Space Physics · Physics 2025-09-29 Vadim Roytershteyn , Lynn B. Wilson , Li-Jen Chen , Michael Gedalin , Nikolai Pogorelov

Particle in cell (PIC) simulations of collisionless magnetic reconnection are presented that demonstrate that the electron dissipation region develops a distinct two-scale structure along the outflow direction. The length of the electron…

Plasma Physics · Physics 2009-11-13 M. A. Shay , J. F. Drake , M. Swisdak

A shock wave propagating perpendicularly to an ambient magnetic field accelerates particles considerably faster than in the parallel propagation regime. However, the perpendicular acceleration stops after the shock overruns a circular…

High Energy Astrophysical Phenomena · Physics 2023-02-06 Mikhail Malkov , Martin Lemoine

In the Universe matter outside of stars and compact objects is mostly composed of collisionless plasma. The interaction of a supersonic plasma flow with an obstacle results in collisionless shocks that are often associated with intense…

Plasma Physics · Physics 2022-05-18 Artem Bohdan , Martin S. Weidl , Paul J. Morris , Martin Pohl

A bounded plasma where the electrons impacting the walls produce more than one secondary on average is studied via particle-in-cell simulation. It is found that no classical Debye sheath or space-charge limited sheath exists. Ions are not…

Plasma Physics · Physics 2015-06-04 M. D. Campanell , A. Khrabrov , I. D. Kaganovich

A thorough understanding of collisionless shocks requires knowledge of how different ion species are accelerated across the shock. We investigate a bow shock crossing using the Magnetospheric Multiscale spacecraft after a coronal mass…

We consider a bilayer of dipolar bosons in which the polarization of dipoles are perpendicular to the planes. Using accurate static structure factor $S(q)$ data from hypernetted-chain calculation for single layer dipolar bosons we construct…

Quantum Gases · Physics 2015-07-23 E. Akaturk , B. Tanatar , Saeed H. Abedinpour

Collisionless shocks are one of the most powerful particle accelerators in the Universe. In the heliosphere, type II solar radio bursts are signatures of electrons accelerated by collisionless shocks launched at the Sun. Spectral…

Solar and Stellar Astrophysics · Physics 2025-02-25 D. E. Morosan , I. C. Jebaraj , P. Zhang , P. Zucca , B. Dabrowski , P. T. Gallagher , A. Krankowski , C. Vocks , R. Vainio

We study a relativistic collisionless electron-positron shock propagating into an unmagnetized ambient medium using 2D particle-in-cell simulations of unprecedented duration and size. The shock generates intermittent magnetic structures of…

High Energy Astrophysical Phenomena · Physics 2024-03-12 Daniel Groselj , Lorenzo Sironi , Anatoly Spitkovsky

We present results from three-dimensional particle simulations of collisionless shocks with relativistic counter-streaming ion-electron plasmas. Particles are followed over many skin depths downstream of the shock. Open boundaries allow the…

Astrophysics · Physics 2009-11-10 J. Trier Frederiksen , C. B. Hededal , T. Haugboelle , A. Nordlund

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