Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows
Electron-scale Kelvin–Helmholtz instabilities (ESKHIs) are found in several astrophysical scenarios. Naturally, ESKHIs are subject to a background magnetic field, but an analytical dispersion relation and an accurate growth rate of ESKHI under this circumstance have remained open because former magn...
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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/ade3cf |
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| author | Yao Guo Dong Wu Jie Zhang |
| author_facet | Yao Guo Dong Wu Jie Zhang |
| author_sort | Yao Guo |
| collection | DOAJ |
| description | Electron-scale Kelvin–Helmholtz instabilities (ESKHIs) are found in several astrophysical scenarios. Naturally, ESKHIs are subject to a background magnetic field, but an analytical dispersion relation and an accurate growth rate of ESKHI under this circumstance have remained open because former magnetohydrodynamics derivations are not applicable in the relativistic regime. We present a generalized dispersion relation of ESKHI in relativistic magnetized shear flows, with two-fluid equations in the cold limit. ESKHI linear growth rates in certain cases are numerically calculated. The results show that when the shear velocity is relatively small, the presence of an external magnetic field results in a decreased maximum instability growth rate, a larger cutoff wavenumber of the unstable band, and an increased wavenumber of the most unstable mode. However, when the shear velocity is sufficiently high, the external magnetic field can increase the maximum instability growth rate instead. Particle-in-cell simulations are also carried out to verify our conclusions. In simulations, we observe the generation of a kinetic direct-current (DC) magnetic field, which is shown to have a strong impact on ESKHIs. In the presence of an external magnetic field, the DC magnetic field generation is suppressed because of electron gyration across the shear interface. Beyond the stabilizing threshold external magnetic field predicted by our fluid theory, we further observe possible evidence of Weibel instabilities. |
| format | Article |
| id | doaj-art-580c9d322bcf4cebbc235dd86d1a07a7 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-580c9d322bcf4cebbc235dd86d1a07a72025-08-20T02:50:03ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01988214710.3847/1538-4357/ade3cfElectron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear FlowsYao Guo0https://orcid.org/0009-0009-7523-5887Dong Wu1https://orcid.org/0000-0001-5738-5739Jie Zhang2https://orcid.org/0000-0001-7821-4808State Key Laboratory of Dark Matter Physics, Key Laboratory for Laser Plasmas (MoE), Department of Physics and Astronomy, Shanghai Jiao Tong University , Shanghai 200240, People’s Republic of China ; dwu.phys@sjtu.edu.cn, jzhang1@sjtu.edu.cnState Key Laboratory of Dark Matter Physics, Key Laboratory for Laser Plasmas (MoE), Department of Physics and Astronomy, Shanghai Jiao Tong University , Shanghai 200240, People’s Republic of China ; dwu.phys@sjtu.edu.cn, jzhang1@sjtu.edu.cn; Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University , Shanghai 200240, People's Republic of ChinaState Key Laboratory of Dark Matter Physics, Key Laboratory for Laser Plasmas (MoE), Department of Physics and Astronomy, Shanghai Jiao Tong University , Shanghai 200240, People’s Republic of China ; dwu.phys@sjtu.edu.cn, jzhang1@sjtu.edu.cn; Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiao Tong University , Shanghai 200240, People's Republic of China; Tsung-Dao Lee Institute, Shanghai Jiao Tong University , Shanghai 201210, People’s Republic of ChinaElectron-scale Kelvin–Helmholtz instabilities (ESKHIs) are found in several astrophysical scenarios. Naturally, ESKHIs are subject to a background magnetic field, but an analytical dispersion relation and an accurate growth rate of ESKHI under this circumstance have remained open because former magnetohydrodynamics derivations are not applicable in the relativistic regime. We present a generalized dispersion relation of ESKHI in relativistic magnetized shear flows, with two-fluid equations in the cold limit. ESKHI linear growth rates in certain cases are numerically calculated. The results show that when the shear velocity is relatively small, the presence of an external magnetic field results in a decreased maximum instability growth rate, a larger cutoff wavenumber of the unstable band, and an increased wavenumber of the most unstable mode. However, when the shear velocity is sufficiently high, the external magnetic field can increase the maximum instability growth rate instead. Particle-in-cell simulations are also carried out to verify our conclusions. In simulations, we observe the generation of a kinetic direct-current (DC) magnetic field, which is shown to have a strong impact on ESKHIs. In the presence of an external magnetic field, the DC magnetic field generation is suppressed because of electron gyration across the shear interface. Beyond the stabilizing threshold external magnetic field predicted by our fluid theory, we further observe possible evidence of Weibel instabilities.https://doi.org/10.3847/1538-4357/ade3cfRelativistic jetsPlasma jetsPlasma physicsMagnetic fields |
| spellingShingle | Yao Guo Dong Wu Jie Zhang Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows The Astrophysical Journal Relativistic jets Plasma jets Plasma physics Magnetic fields |
| title | Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows |
| title_full | Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows |
| title_fullStr | Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows |
| title_full_unstemmed | Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows |
| title_short | Electron-scale Kelvin–Helmholtz Instabilities in Magnetized Shear Flows |
| title_sort | electron scale kelvin helmholtz instabilities in magnetized shear flows |
| topic | Relativistic jets Plasma jets Plasma physics Magnetic fields |
| url | https://doi.org/10.3847/1538-4357/ade3cf |
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