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Shockwaves in plasma are usually dealt with using Magnetohydrodynamics (MHD). Yet, MHD entails the assumption of a short mean free path, which is not fulfilled in a collisionless plasma. Recently, for pair plasmas, we devised a model…

Plasma Physics · Physics 2023-01-04 Antoine Bret , Ramesh Narayan

The properties of collisionless shocks are frequently assessed in the magnetohydrodynamics (MHD) model. Yet, in a collisionless plasma, an ambient magnetic field can sustain a stable anisotropy in the upstream or the downstream, resulting…

Plasma Physics · Physics 2023-03-08 Antoine Bret

In the absence of frequent binary collisions to isotropize the plasma, the fulfillment of the magnetohydrodynamic (MHD) Rankine-Hugoniot jump conditions by collisionless shocks is not trivial. In particular, the presence of an external…

Plasma Physics · Physics 2019-06-26 Antoine Bret , Ramesh Narayan

Collisionless shocks are frequently analyzed using the magnetohydrodynamics (MHD) formalism, even though MHD assumes a small mean free path. Yet, isotropy of pressure, fruit of binary collisions and assumed in MHD, may not apply in…

Plasma Physics · Physics 2024-03-05 Antoine Bret , Colby C. Haggerty , Ramesh Narayan

Within the context of Magnetohydrodynamics (MHD), the properties of a parallel shock do not depend on the field strength, as the field and the fluid are disconnected for such a geometry. However, in the collisionless case, the field can…

Plasma Physics · Physics 2021-08-25 Antoine Bret

Collisionless shocks follow the Rankine-Hugoniot jump conditions to a good approximation. However, for a shock propagating parallel to a magnetic field, magnetohydrodynamics states that the shock properties are independent of the field…

Plasma Physics · Physics 2018-12-26 Antoine Bret , Ramesh Narayan

Collisionless shocks are frequently analyzed using the magnetohydrodynamic formalism (MHD), even though the required collisionality hypothesis is not fulfilled. In a previous work \citep{BretJPP2018}, we presented a model of collisionless…

Plasma Physics · Physics 2025-06-10 Antoine Bret , Ramesh Narayan

When applied to compute the density jump of a shock, the standard magnetohydrodynamic (MHD) formalism assumes, 1) that all the upstream material passes downstream, together with the momentum and energy it carries, and 2) that pressures are…

Plasma Physics · Physics 2020-07-15 Antoine Bret

Shock waves are common in astrophysical environments. On many occasions, they are collisionless, which means they occur in settings where the mean free path is much larger than the dimensions of the system. For this very reason,…

Plasma Physics · Physics 2023-07-12 Antoine Bret

According to magnetohydrodynamics (MHD), the encounter of two collisional magnetized plasmas at high velocity gives rise to shock waves. Investigations conducted so far have found that the same conclusion still holds in the case of…

Plasma Physics · Physics 2017-05-24 Antoine Bret , Asaf Pe'er , Lorenzo Sironi , Aleksander Sadowski , Ramesh Narayan

Shocks waves are a ubiquitous feature of many astrophysical plasma systems, and an important process for energy dissipation and transfer. The physics of these shock waves are frequently treated/modeled as a collisional, fluid MHD…

Plasma Physics · Physics 2021-11-17 Colby C. Haggerty , Antoine Bret , Damiano Caprioli

Collisionless electron-ion shocks are fundamental to astrophysical plasmas, yet their behavior in strong magnetic fields remains poorly understood. Using Particle-in-Cell (PIC) simulations with the SHARP-1D3V code, we investigate the role…

Solar and Stellar Astrophysics · Physics 2025-11-17 Mohamad Shalaby , Antoine Bret , Federico Fraschetti

Shock waves constitute discontinuities in matter which are relevant in studying the plasma behaviour in astrophysical scenarios and in heavy-ion collision. They can produce conical emission in relativistic collisions and are also thought to…

High Energy Astrophysical Phenomena · Physics 2013-09-03 Ritam Mallick , Stefan Schramm

Magnetized collisionless shocks drive particle acceleration broadly in space and astrophysics. We perform the first large-scale particle-in-cell simulations with realistic laboratory parameters (density, temperature, and velocity) to…

Plasma Physics · Physics 2024-05-24 P. Liu , D. Wu , D. W. Yuan , G. Zhao , Z. M. Sheng , X. T. He , J. Zhang

The amplification and maintenance of the observed magnetic fields in the ICM are usually attributed to the turbulent dynamo action. This is generally derived employing a collisional MHD model. However, in the ICM the ion mean free path…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 R. Santos-Lima , E. M. de Gouveia Dal Pino , G. Kowal , D. Falceta-Gonçalves , A. Lazarian , M. S. Nakwacki

A pair of curved shocks in a collisionless plasma is examined with a two-dimensional particle-in-cell (PIC) simulation. The shocks are created by the collision of two electron-ion clouds at a speed that exceeds everywhere the threshold…

High Energy Astrophysical Phenomena · Physics 2015-07-14 M. E. Dieckmann , A. Bock , H. Ahmed , D. Doria , G. Sarri , A. Ynnerman , M. Borghesi

The role of slow-mode MHD shocks in magnetic reconnection is one of great importance for energy conversion and transport, but in many astrophysical plasmas the plasma is not fully ionised. In this paper, we investigate, using numerical…

Solar and Stellar Astrophysics · Physics 2016-10-27 Andrew Hillier , Shinsuke Takasao , Naoki Nakamura

The research is aimed at the study of the properties of solutions for parallel MHD shock waves in collisionless plasma with heat fluxes, using 8-moment MHD approximation. Restrictions have been established on the upstream shock parameters…

Plasma Physics · Physics 2020-03-24 V. D. Kuznetsov , A. I. Osin

Results from a numerical study of fluctuation dynamo in a collisionless, weakly magnetized plasma are presented. The key difference between this dynamo and its magnetohydrodynamic (MHD) counterpart is the adiabatic production of…

High Energy Astrophysical Phenomena · Physics 2018-08-17 Denis A. St-Onge , Matthew W. Kunz

We explore analytically the structure of relativistic shock and solitary wave solutions in collisionless plasmas. In the wave frame of reference, a cold plasma is flowing from one end and impacting on a low velocity plasma. First we show…

Astrophysics · Physics 2007-05-23 David Medvigy , Abraham Loeb
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