Gyrokinetic study of multiple electrostatic and electromagnetic electron-temperature-gradient modes and relevant transport in tokamak finite βe plasmas
We present a comprehensive study of the multiple electrostatic and electromagnetic electron temperature gradient (ETG) modes with a significant upgrading of the gyrokinetic code HD7. Specifically, the non-adiabaticity of all particle species and the electromagnetic effects are taken into account in...
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| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | Nuclear Fusion |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1741-4326/adc01b |
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| Summary: | We present a comprehensive study of the multiple electrostatic and electromagnetic electron temperature gradient (ETG) modes with a significant upgrading of the gyrokinetic code HD7. Specifically, the non-adiabaticity of all particle species and the electromagnetic effects are taken into account in the upgraded version. Multiple electrostatic ETG (ES-ETG) modes with conventional and unconventional ballooning mode structures are found to be excited by large temperature gradients. The unconventional modes with mode-index $l$ >0 (where $l$ represents peak number as well as parity in ballooning space) have comparable growth rates with the conventional mode under the specific condition, e.g. $6 < R/{L_{Te}} < 25$ , indicating that unconventional modes are significant in L-mode or pedestal top of H-mode. In addition, different from the phenomenon of ES-ETG, multiple electromagnetic ETG (EM-ETG) modes can be excited with ${k_\vartheta }{\rho _s} > 1$ and the transition of the dominant eigenstate is observed. The $l = 1$ EM-ETG mode has an excited threshold of ${\beta _e} = 0.006$ (the ratio of electron pressure over magnetic pressure), indicating that the electromagnetic effect plays a key role in high $\beta $ (the ratio of thermal pressure to magnetic pressure) condition. Similar to the typical ES-ETG mode, the novel EM-ETG mode is destabilized by large $R/{L_{Te}}$ and suppressed by sufficiently large (either positive or negative) magnetic shear. Talking about the transport capability, the simulation result reveals that EM-ETG mode induced particle flux is quite low ( ${{{\Gamma }}_{{\text{ES}} - {\text{ETG}}}} \ll {{{\Gamma }}_{{\text{EM}} - {\text{ETG}}}} \ll {{{\Gamma }}_{{\text{ITG}}}}$ ) while the energy flux is non-negligible compared to that induced by ion temperature gradient driven mode. Possible relevance of the results with the transport physics in transport barriers is discussed. |
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| ISSN: | 0029-5515 |