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We study the impulsively generated non-linear Alfv\'en waves in the solar atmosphere, and describe their most likely role in the observed non-thermal broadening of some spectral lines in solar coronal holes. We solve numerically the…

Solar and Stellar Astrophysics · Physics 2015-06-05 P. Chmielewski , A. K. Srivastava , K. Murawski , Z. E. Musielak

We have modeled the simultaneous first-order Fermi shock acceleration of protons, electrons, and helium nuclei by relativistic shocks. By parameterizing the particle diffusion, our steady-state Monte Carlo simulation allows us to follow…

High Energy Astrophysical Phenomena · Physics 2015-07-15 Donald C. Warren , Donald C. Ellison , Andrei M. Bykov , Shiu-Hang Lee

A new particle acceleration process in a developing Alfv\'{e}n turbulence in the course of successive parametric instabilities of a relativistic pair plasma is investigated by utilyzing one-dimensional electromagnetic full particle code.…

High Energy Astrophysical Phenomena · Physics 2014-11-20 S. Matsukiyo , T. Hada

We report the first experimental detection of a reflected Alfv\'en wave from an Alfv\'en-speed gradient under conditions similar to those in coronal holes. The experiments were conducted in the Large Plasma Device at the University of…

The analysis of energy balance of coronal holes gives that to accelerate the fast solar wind streams the energy flux of the order of 800 erg/cm$^2$ s is needed. Axford and McKenzie suggested that the energy source, necessary to accelerate…

Plasma Physics · Physics 2007-05-23 Andrei Sadovski

We extend the eigenfunction method of computing the power-law spectrum of particles accelerated at a relativistic shock fronts to apply to shocks of arbitrarily high Lorentz factor. In agreement with the findings of Monte-Carlo simulations,…

Astrophysics · Physics 2009-10-31 J. G. Kirk , A. W. Guthmann , Y. A. Gallant , A. Achterberg

We have studied the propagation of inertial Alfv\'en waves through parallel gradients in the Alfv\'en speed using the Large Plasma Device at the University of California, Los Angeles. The reflection and transmission of Alfv\'en waves…

We present a survey of 1D kinetic particle-in-cell simulations of quasi-parallel non-relativistic shocks to identify the environments favorable for electron acceleration. We explore an unprecedented range of shock speeds $v_{\rm sh}\approx…

High Energy Astrophysical Phenomena · Physics 2024-08-30 Siddhartha Gupta , Damiano Caprioli , Anatoly Spitkovsky

Diffusive acceleration at collisionless shock waves remains one of the most promising acceleration mechanisms for the description of the origin of cosmic rays at all energies. A crucial ingredient to be taken into account is the reaction of…

Astrophysics · Physics 2009-11-13 Elena Amato , Pasquale Blasi

We apply a semi-classical approach of handling waves as quasiparticle gas in a slowly varying flow -- analogous to ray tracing -- to calculate the Alfven wave transmission parameters, the resulting cross-helicity of the waves and the…

Astrophysics · Physics 2007-05-23 Joni Tammi , Rami Vainio

We investigate the mechanism of whistler-mode wave generation by shock-reflected electrons at quasi-perpendicular collisionless shocks. By employing Liouville mapping to construct the electron velocity distribution function in the shock and…

Plasma Physics · Physics 2026-03-20 Ruolin Wang , Takanobu Amano

A simplified model of particle transport at a quasiparallel one-dimensional collisionless shock is suggested. In this model the MHD-turbulence behind the shock is dominated by a circularly polarized, large amplitude Alfv\'en wave originated…

Astrophysics · Physics 2008-11-26 M. A. Malkov

The process of diffusive shock acceleration relies on the efficacy with which hydromagnetic waves can scatter charged particles in the precursor of a shock. The growth of self-generated waves is driven by both resonant and non-resonant…

Astrophysics · Physics 2009-11-13 B. Reville , S. O'Sullivan , P. Duffy , J. G. Kirk

We propose a particle acceleration mechanism driven by large-amplitude Alfv\'en waves in a strong magnetic field. The acceleration process proceeds through multiple stages triggered by counterpropagating wave-particle resonant acceleration…

Plasma Physics · Physics 2025-11-06 S. Isayama , S. Matsukiyo , T. Sano , S. H. Chen

First-order Fermi acceleration processes at ultrarelativistic shocks are studied with Monte Carlo simulations. The accelerated particle spectra are obtained by integrating the exact particle trajectories in a turbulent magnetic field near…

Astrophysics · Physics 2009-11-13 Jacek Niemiec

Diffusive shock acceleration at collisionless shocks remains the most likely process for accelerating particles in a variety of astrophysical sources. While the standard prediction for strong shocks is that the spectrum of accelerated…

High Energy Astrophysical Phenomena · Physics 2025-12-15 Pierre Cristofari , Pasquale Blasi , Damiano Caprioli

We use large hybrid (kinetic protons-fluid electrons) simulations to investigate the transport of energetic particles in self-consistent electromagnetic configurations of collisionless shocks. In previous papers of this series, we showed…

High Energy Astrophysical Phenomena · Physics 2015-06-22 Damiano Caprioli , Anatoly Spitkovsky

We present evidence that relativistic shocks propagating in unmagnetized plasmas can self-consistently accelerate particles. We use long-term two-dimensional particle-in-cell simulations to study the well-developed shock structure in…

Astrophysics · Physics 2009-11-13 Anatoly Spitkovsky

Strong magnetically dominated Alfv\'enic turbulence is an efficient engine of non-thermal particle acceleration in a relativistic collisionless plasma. We argue that in the limit of strong magnetization, the type of energy distribution…

Plasma Physics · Physics 2024-05-14 Cristian Vega , Stanislav Boldyrev , Vadim Roytershteyn

We study the acceleration of electrons and positrons at an electromagnetically modified, ultra-relativistic shock in the context of pulsar wind nebulae (PWNe). We simulate the outflow produced by an obliquely rotating pulsar in proximity of…

High Energy Astrophysical Phenomena · Physics 2017-02-08 Simone Giacchè , John G. Kirk