Magnetic island dynamic with current sheet and turbulence
Event details
| Date | 28.01.2013 |
| Hour | 10:30 › 11:30 |
| Speaker | Alexandre Poyé, Université de Provence, Marseille, F |
| Location |
PPB 019
|
| Category | Conferences - Seminars |
Magnetic islands are a source of damage in tokamaks and their control by injection of external control current requires an ever growing understanding of the physical processes [Commisso et al, Nucl. Fusion, 125002 (2010)]. The nonlinear evolution of magnetic islands is investigated by means of numerical simulations.
First, we show that classical boundary layer analysis, leading to Rutherford like equations, may not capture the island width dynamics generated by tearing instability. We underline the importance of the initial global current profile. Indeed, nonlocal effects of a finite current density away from the resonant surface can significantly alter the island growth and saturation. The underlying mechanisms linked to the generation of vorticity by interacting current sheets, including island separatrices, are presented.
Second, we address the problem of the generation of seed magnetic islands by turbulence [Muraglia et al, Phys. Rev. Lett., 095003 (2011)], which is relevant in NTM context. We show - and present the different mechanisms at play - that turbulence can spread out into stable regions where for instance low order rational surface q=2 is available and drive the generation of m/n=2/1 island. It gives some support to the observation that magnetic island do appear only at low order rational surface.
First, we show that classical boundary layer analysis, leading to Rutherford like equations, may not capture the island width dynamics generated by tearing instability. We underline the importance of the initial global current profile. Indeed, nonlocal effects of a finite current density away from the resonant surface can significantly alter the island growth and saturation. The underlying mechanisms linked to the generation of vorticity by interacting current sheets, including island separatrices, are presented.
Second, we address the problem of the generation of seed magnetic islands by turbulence [Muraglia et al, Phys. Rev. Lett., 095003 (2011)], which is relevant in NTM context. We show - and present the different mechanisms at play - that turbulence can spread out into stable regions where for instance low order rational surface q=2 is available and drive the generation of m/n=2/1 island. It gives some support to the observation that magnetic island do appear only at low order rational surface.
Practical information
- Expert
- Free
Organizer
- Prof. P. Ricci
Contact
- Prof. P. Ricci