Collisionless Shocks Having Relativistic Velocities in Relativistically Hot Plasmas
Shocks in relativistically hot plasmas are thought to exist in various high-energy astrophysical phenomena, but it is not clear how relativistic collisionless shocks are formed, and whether particles are accelerated by the shock as in the case of cold upstream. In this work, collisionless shocks wit...
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IOP Publishing
2025-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/adced6 |
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| author | Kazuki Kamiido Yutaka Ohira |
| author_facet | Kazuki Kamiido Yutaka Ohira |
| author_sort | Kazuki Kamiido |
| collection | DOAJ |
| description | Shocks in relativistically hot plasmas are thought to exist in various high-energy astrophysical phenomena, but it is not clear how relativistic collisionless shocks are formed, and whether particles are accelerated by the shock as in the case of cold upstream. In this work, collisionless shocks with a relativistic shock velocity in relativistically hot, unmagnetized electron–positron plasmas are investigated by two-dimensional particle-in-cell simulations. It is shown that the upstream flow is dissipated by the Weibel instability, so that the relativistic collisionless shock is formed as in the case of cold upstream. The density and magnetic field structures around the shock front are almost independent of the upstream temperature when the spatial scale is normalized by the inertial length scale, which takes into account the relativistic temperature. This can be understood by considering the pressure anisotropy, which asymptotically approaches a finite value due to the relativistic beaming effect, even as the temperature becomes relativistically hotter and hotter. In addition, as long as the shock velocity is relativistic, some particles are accelerated, forming a power-law energy spectrum similar to that in the cold upstream. |
| format | Article |
| id | doaj-art-411f74da4b544bfb8d819dd3a23f66ba |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-411f74da4b544bfb8d819dd3a23f66ba2025-08-20T01:55:12ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01985113410.3847/1538-4357/adced6Collisionless Shocks Having Relativistic Velocities in Relativistically Hot PlasmasKazuki Kamiido0https://orcid.org/0009-0002-9063-8827Yutaka Ohira1https://orcid.org/0000-0002-2387-0151Department of Earth and Planetary Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan ; kamiido-kazuki8990@g.ecc.u-tokyo.ac.jpDepartment of Earth and Planetary Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan ; kamiido-kazuki8990@g.ecc.u-tokyo.ac.jpShocks in relativistically hot plasmas are thought to exist in various high-energy astrophysical phenomena, but it is not clear how relativistic collisionless shocks are formed, and whether particles are accelerated by the shock as in the case of cold upstream. In this work, collisionless shocks with a relativistic shock velocity in relativistically hot, unmagnetized electron–positron plasmas are investigated by two-dimensional particle-in-cell simulations. It is shown that the upstream flow is dissipated by the Weibel instability, so that the relativistic collisionless shock is formed as in the case of cold upstream. The density and magnetic field structures around the shock front are almost independent of the upstream temperature when the spatial scale is normalized by the inertial length scale, which takes into account the relativistic temperature. This can be understood by considering the pressure anisotropy, which asymptotically approaches a finite value due to the relativistic beaming effect, even as the temperature becomes relativistically hotter and hotter. In addition, as long as the shock velocity is relativistic, some particles are accelerated, forming a power-law energy spectrum similar to that in the cold upstream.https://doi.org/10.3847/1538-4357/adced6High energy astrophysicsPlasma astrophysicsPlasma physicsShocksGamma-ray bursts |
| spellingShingle | Kazuki Kamiido Yutaka Ohira Collisionless Shocks Having Relativistic Velocities in Relativistically Hot Plasmas The Astrophysical Journal High energy astrophysics Plasma astrophysics Plasma physics Shocks Gamma-ray bursts |
| title | Collisionless Shocks Having Relativistic Velocities in Relativistically Hot Plasmas |
| title_full | Collisionless Shocks Having Relativistic Velocities in Relativistically Hot Plasmas |
| title_fullStr | Collisionless Shocks Having Relativistic Velocities in Relativistically Hot Plasmas |
| title_full_unstemmed | Collisionless Shocks Having Relativistic Velocities in Relativistically Hot Plasmas |
| title_short | Collisionless Shocks Having Relativistic Velocities in Relativistically Hot Plasmas |
| title_sort | collisionless shocks having relativistic velocities in relativistically hot plasmas |
| topic | High energy astrophysics Plasma astrophysics Plasma physics Shocks Gamma-ray bursts |
| url | https://doi.org/10.3847/1538-4357/adced6 |
| work_keys_str_mv | AT kazukikamiido collisionlessshockshavingrelativisticvelocitiesinrelativisticallyhotplasmas AT yutakaohira collisionlessshockshavingrelativisticvelocitiesinrelativisticallyhotplasmas |