Relaxation to universal non-Maxwellian equilibria in a collisionless plasma
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arXiv
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| Auteurs principaux: | , , , , , |
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| Format: | Preprint |
| Publié: |
2024
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| _version_ | 1866916380025028608 |
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| author | Ewart, Robert J. Nastac, Michael L. Bilbao, Pablo J. Silva, Thales Silva, Luís O. Schekochihin, Alexander A. |
| author_facet | Ewart, Robert J. Nastac, Michael L. Bilbao, Pablo J. Silva, Thales Silva, Luís O. Schekochihin, Alexander A. |
| contents | Generic equilibria are derived for turbulent relaxing plasmas via an entropy-maximization procedure that accounts for the short-time conservation of certain collisionless invariants. The conservation of these collisionless invariants endows the system with a partial `memory' of its prior conditions, but is imperfect on long time scales due to the development of a turbulent cascade to small scales, which breaks the precise conservation of phase volume, making this memory imprecise. The equilibria are still determined by the short-time collisionless invariants, but the invariants themselves are driven to a universal form by the nature of the turbulence. This is numerically confirmed for the case of beam instabilities in one-dimensional electrostatic plasmas, where sufficiently strong turbulence appears to cause the distribution function of particle energies to develop a universal power-law tail, with exponent -2. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2409_01742 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Relaxation to universal non-Maxwellian equilibria in a collisionless plasma Ewart, Robert J. Nastac, Michael L. Bilbao, Pablo J. Silva, Thales Silva, Luís O. Schekochihin, Alexander A. Plasma Physics High Energy Astrophysical Phenomena Statistical Mechanics Generic equilibria are derived for turbulent relaxing plasmas via an entropy-maximization procedure that accounts for the short-time conservation of certain collisionless invariants. The conservation of these collisionless invariants endows the system with a partial `memory' of its prior conditions, but is imperfect on long time scales due to the development of a turbulent cascade to small scales, which breaks the precise conservation of phase volume, making this memory imprecise. The equilibria are still determined by the short-time collisionless invariants, but the invariants themselves are driven to a universal form by the nature of the turbulence. This is numerically confirmed for the case of beam instabilities in one-dimensional electrostatic plasmas, where sufficiently strong turbulence appears to cause the distribution function of particle energies to develop a universal power-law tail, with exponent -2. |
| title | Relaxation to universal non-Maxwellian equilibria in a collisionless plasma |
| topic | Plasma Physics High Energy Astrophysical Phenomena Statistical Mechanics |
| url | https://arxiv.org/abs/2409.01742 |