Structure of Micro-instabilities in Tokamak Plasmas: Stiff Transport or Plasma Eruptions?
| Autor: | Dickinson, D., Roach, C. M., Skipp, J. M., Wilson, H. R. |
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| Rok vydání: | 2014 |
| Předmět: | |
| Zdroj: | Phys. Plasmas 21, 010702 (2014) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1063/1.4861628 |
| Popis: | Solutions to a model 2D eigenmode equation describing micro-instabilities in tokamak plasmas are presented that demonstrate a sensitivity of the mode structure and stability to plasma profiles. In narrow regions of parameter space, with special plasma profiles, a maximally unstable mode is found that balloons on the outboard side of the tokamak. This corresponds to the conventional picture of a ballooning mode. However, for most profiles this mode cannot exist and instead a more stable mode is found that balloons closer to the top or bottom of the plasma. Good quantitative agreement with a 1D ballooning analysis is found provided the constraints associated with higher order profile effects, often neglected, are taken into account. A sudden transition from this general mode to the more unstable ballooning mode can occur for a critical flow shear, providing a candidate model for why some experiments observe small plasma eruptions (Edge Localised Modes, or ELMs) in place of large Type I ELMs. Comment: 11 pages, 3 figures |
| Databáze: | arXiv |
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