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The most stringent test of theoretical models of the first-order Fermi mechanism at collisionless astrophysical shocks is a comparison of the theoretical predictions with observational data on particle populations. Such comparisons have…

Astrophysics · Physics 2009-10-28 Matthew G. Baring , Keith Ogilvie , Donald Ellison , Robert Forsyth

Shock accelerated electrons are found in many astrophysical environments, and the mechanisms by which they are accelerated to high energies are still not completely clear. For relatively high Mach numbers, the shock is supercritical, and…

Space Physics · Physics 2018-10-17 D. Trotta , D. Burgess

Using test particle simulations we study particle acceleration at highly perpendicular ($\theta_{Bn}\geq 75^\circ$) shocks under conditions of modeling magnetic turbulence. We adopt a backward-in-time method to solve the Newton-Lorentz…

Space Physics · Physics 2017-08-23 F. -J. Kong , G. Qin , L. -H. Zhang

Solar wind ion reflection at collisionless shocks regulates foreshock plasma dynamics, yet the quantitative dependence of reflected ion properties on upstream and shock-related parameters remains unclear, causing difficulties in predicting…

Space Physics · Physics 2026-03-30 Runyi Liu , Terry Liu , Kun Zhang , Vassilis Angelopoulos , Siqi Zhao

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

Shocks associated with Interplanetary Coronal Mass Ejections are known to energize charged particles and give rise to Solar Energetic Particles. Many of these energetic particles move ahead of the shock to create a foreshock region. The…

Solar and Stellar Astrophysics · Physics 2025-04-30 Shanwlee Sow Mondal , Aveek Sarkar , Sofiane Bourouaine

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

Turbulence in space plasmas usually exhibits two regimes separated by a spectral break that divides the so called inertial and kinetic ranges. Large scale magnetic fluctuations are dominated by non-linear MHD wave-wave interactions…

Plasma Physics · Physics 2021-03-22 Pablo S. Moya , Roberto E. Navarro

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

We study how a high-speed solar wind stream embedded in a slow solar wind influences the spread of solar energetic protons in interplanetary space. To model the energetic protons, we used a recently developed particle transport code that…

Space Physics · Physics 2019-04-10 Nicolas Wijsen , Angels Aran , Jens Pomoell , Stefaan Poedts

Collisionless shocks heat electrons in the solar wind, interstellar blast waves, and hot gas permeating galaxy clusters. How much shock heating goes to electrons instead of ions, and what plasma physics controls electron heating? We…

Space Physics · Physics 2021-01-01 Aaron Tran , Lorenzo Sironi

We explore the physics of shock evolution and particle acceleration in non-relativistic collisionless shocks using multidimensional hybrid simulations. We analyze a wide range of physical parameters relevant to the acceleration of cosmic…

High Energy Astrophysical Phenomena · Physics 2015-05-28 L. Gargaté , A. Spitkovsky

This study aims to investigate the relationship between the spatial-temporal evolution of shock properties and the longitudinal dependence of SEP intensities and spectra. The shock parameters, including the normal speed, oblique angles,…

Solar and Stellar Astrophysics · Physics 2026-01-21 Yue Zhou , Li Feng , Guanglu Shi , Jingnan Guo , Liuguan Ding , Yi Yang , Jianchao Xue , Jun Chen , Weiqun Gan

Charged particles can be accelerated to high energies by collisionless shock waves in astrophysical environments, such as supernova remnants. By interacting with the magnetized ambient medium, these shocks can transfer energy to particles.…

Shocks in astrophysical transients are key sites of particle acceleration. If the shock upstream is optically thick, radiation smoothens the velocity discontinuity at the shock (radiation-mediated shocks). However, in mildly magnetized…

High Energy Astrophysical Phenomena · Physics 2026-05-12 Shunke Ai , Irene Tamborra

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

We investigate the interaction of nonthermal ions (protons and nuclei) accelerated in an ultrarelativistic blastwave with the pre-existing magnetic field of the medium into which the blastwave propagates. While particle acceleration…

Astrophysics · Physics 2009-11-13 Sean M. Couch , Milos Milosavljevic , Ehud Nakar

Energetic particles in interplanetary space are normally measured at time scales that are long compared to the ion gyroperiod. Such observations by necessity average out the microphysics associated with the acceleration and transport of 10s…

The Magnetic cloud boundary layer (BL) is a dynamic region formed by the interaction of the magnetic cloud (MC) and the ambient solar wind. In the present study, we comparatively investigate the proton and electron mean flux variations in…

Space Physics · Physics 2012-06-26 Y. Wang , F. S. Wei , X. S. Feng , P. B. Zuo , J. P. Guo , X. J. Xu , Z. Li

Collisionless shock waves, found in supernova remnants, interstellar, stellar, and planetary environments, and laboratories, are one of nature's most powerful particle accelerators. This study combines in situ satellite measurements with…

High Energy Astrophysical Phenomena · Physics 2025-03-05 Savvas Raptis , Ahmad Lalti , Martin Lindberg , Drew L. Turner , Damiano Caprioli , James L. Burch