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Acceleration of particles and plasma heating is one of the fundamental problems in solar flare physics. An accurate determination of the spectrum of flare energized electrons over a broad energy range is crucial for our understanding of…

Solar and Stellar Astrophysics · Physics 2015-12-16 Marina Battaglia , Galina Motorina , Eduard P. Kontar

These notes present the fundamentals of Fermi acceleration at shocks, with a special attention to the role that supernova remnants have in producing Galactic cosmic rays. Then, the recent discoveries in the theory of diffusive shock…

High Energy Astrophysical Phenomena · Physics 2023-10-09 Damiano Caprioli

Energetic positrons have been observed in the interstellar medium, and high-energy positrons with relativistic energies up to approximately 1 TeV have been detected in Galactic cosmic rays. We conducted a study on the acceleration of…

High Energy Astrophysical Phenomena · Physics 2024-05-31 Huan Yu , Qi Xia , Jun Fang

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

In addition to electrons and protons, nonrelativistic quasiparallel shocks are expected to possess the ability to accelerate heavy ions. The shocks in supernova remnants are generally supposed to be accelerators of the Galactic cosmic rays,…

High Energy Astrophysical Phenomena · Physics 2022-04-20 Jun Fang , Qi Xia , Shiting Tian , Liancheng Zhou , Huan Yu

From the perspective of non-equilibrium statistical mechanics, modeling the velocity distribution of particles in non-equilibrium, steady-state plasmas presents a significant challenge. Under this context, a family of kappa distributions…

Plasma Physics · Physics 2025-09-10 Abiam Tamburrini , Sergio Davis , Pablo S. Moya

We report on a new Monte Carlo method for simulating diffusive shock acceleration (DSA) of solar energetic particles at upstream and downstream regions of quasi-parallel collisionless shock waves under the influence of self-generated…

Space Physics · Physics 2014-08-14 Arto Sandroos , Gang Li , Lulu Zhao

We study diffusive shock acceleration (DSA) of electrons in non-relativistic quasi-perpendicular shocks using self-consistent one-dimensional particle-in-cell (PIC) simulations. By exploring the parameter space of sonic and Alfv\'{e}nic…

High Energy Astrophysical Phenomena · Physics 2020-07-22 Rui Xu , Anatoly Spitkovsky , Damiano Caprioli

Collisionless shocks with low sonic Mach numbers, $M_{\rm s} \lesssim 4$, are expected to accelerate cosmic ray (CR) protons via diffusive shock acceleration (DSA) in the intracluster medium (ICM). However, observational evidence for CR…

High Energy Astrophysical Phenomena · Physics 2018-10-10 Ji-Hoon Ha , Dongsu Ryu , Hyesung Kang , Allard Jan van Marle

By using the generalized Boltzmann equation of transport and the first-order approximation of Chapman-Enskog expansion on the kappa-distribution function, we study the thermal conductivity and Dufour effects in the weakly ionized and…

Plasma Physics · Physics 2020-03-06 Haijuan Xia , Jiulin Du

Shocks of supernova remnants (SNRs) accelerate charged particles up to 100 TeV range via diffusive shock acceleration (DSA) mechanism. It is believed that shocks of SNRs are the main contributors to the pool of Galactic cosmic rays,…

High Energy Astrophysical Phenomena · Physics 2023-04-05 Jacco Vink , Aya Bamba

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 study the diffusion of charged particles in the weakly ionized plasma with the power-law kappa-distributions and without magnetic field. The electrons and ions have different kappa-parameters. We obtain the expressions of both diffusion…

Plasma Physics · Physics 2020-02-04 Lan Wang , Jiulin Du

We use kinetic simulations of diffusive shock acceleration (DSA) to study the time-dependent evolution of plane, quasi-parallel, cosmic-ray (CR) modified shocks. Thermal leakage injection of low energy CRs and finite Alfv\'en wave…

High Energy Astrophysical Phenomena · Physics 2011-02-11 Hyesung Kang , Dongsu Ryu , T. W. Jones

We examine the test-particle solution for diffusive shock acceleration, based on simple models for thermal leakage injection and Alfv'enic drift. The critical injection rate, \xi_c, above which the cosmic ray (CR) pressure becomes…

High Energy Astrophysical Phenomena · Physics 2015-05-19 Hyesung Kang , Dongsu Ryu

X-ray observations provide important and valuable insights into the acceleration and propagation of nonthermal electrons during solar flares. Improved X-ray spectral analysis requires a deeper understanding of the dynamics of energetic…

Solar and Stellar Astrophysics · Physics 2024-10-15 Yingjie Luo , Eduard P. Kontar , Debesh Bhattacharjee

The acceleration of charged particles by interplanetary shocks (IPs) can drain a non-negligible fraction of the plasma pressure. In this study, we have selected 17 IPs observed in-situ at $1\,\text{au}$ by the Advanced Composition Explorer…

Solar and Stellar Astrophysics · Physics 2022-04-06 Liam David , Federico Fraschetti , Joe Giacalone , Robert F. Wimmer-Schweingruber , Lars Berger , David Lario

The theory of diffusive acceleration of energetic particles at shock fronts assumes charged particles undergo spatial diffusion in a uniform magnetic field. If, however, the magnetic field is not uniform, but has a stochastic or braided…

Astrophysics · Physics 2007-05-23 J. G. Kirk , P. Duffy , Y. A. Gallant

The pseudopotential method is used to derive electron hole structures in a suprathermal plasma having a regularized $\kappa$ probability distribution function background. The regularized character allows the exploration of small $\kappa$…

Plasma Physics · Physics 2023-10-16 Fernando Haas , Horst Fichtner , Klaus Scherer

We demonstrate that a nonthermal distribution of particles described by a kappa distribution can be accurately approximated by a weighted sum of Maxwell-Boltzmann distributions. We apply this method to modeling collision processes in…

Solar and Stellar Astrophysics · Physics 2015-09-09 Michael Hahn , Daniel Wolf Savin