Self-mediation of runaway electrons via self-excited wave-wave and wave-particle interactions
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| Main Authors: | , , , |
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| Format: | Preprint |
| Published: |
2024
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| _version_ | 1866914376762523648 |
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| author | Zhang, Qile Zhang, Yanzeng Tang, Qi Tang, Xian-Zhu |
| author_facet | Zhang, Qile Zhang, Yanzeng Tang, Qi Tang, Xian-Zhu |
| contents | Nonlinear dynamics of runaway electron induced wave instabilities can significantly modify the runaway distribution critical to tokamak operations. Here we present the first-ever fully kinetic simulations of runaway-driven instabilities towards nonlinear saturation in a warm plasma where collisional damping is subdominant. It is found that the slow-X modes grow an order of magnitude faster than the whistler modes, and they parametrically decay to produce whistlers much faster than those directly driven by runaways. These parent-daughter waves, as well as secondary and tertiary wave instabilities, initiate a chain of wave-particle resonances that strongly diffuse runaways to the backward direction. This reduces almost half of the current carried by high-energy runaways, over a time scale orders of magnitude faster than experimental shot duration. These results beyond quasilinear analysis may impact anisotropic energetic electrons broadly in laboratory, space and astrophysics. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2409_15830 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Self-mediation of runaway electrons via self-excited wave-wave and wave-particle interactions Zhang, Qile Zhang, Yanzeng Tang, Qi Tang, Xian-Zhu Plasma Physics Nonlinear dynamics of runaway electron induced wave instabilities can significantly modify the runaway distribution critical to tokamak operations. Here we present the first-ever fully kinetic simulations of runaway-driven instabilities towards nonlinear saturation in a warm plasma where collisional damping is subdominant. It is found that the slow-X modes grow an order of magnitude faster than the whistler modes, and they parametrically decay to produce whistlers much faster than those directly driven by runaways. These parent-daughter waves, as well as secondary and tertiary wave instabilities, initiate a chain of wave-particle resonances that strongly diffuse runaways to the backward direction. This reduces almost half of the current carried by high-energy runaways, over a time scale orders of magnitude faster than experimental shot duration. These results beyond quasilinear analysis may impact anisotropic energetic electrons broadly in laboratory, space and astrophysics. |
| title | Self-mediation of runaway electrons via self-excited wave-wave and wave-particle interactions |
| topic | Plasma Physics |
| url | https://arxiv.org/abs/2409.15830 |