Ideal ballooning stability near an equilibrium magnetic island
- Departments of Nuclear Engineering and Engineering Physics, and Physics, University of Wisconsin, Madison, Wisconsin 53706-1687 (United States)
The stability properties of ideal ballooning modes on toroidal flux surfaces near a quasistatic magnetic island are examined. On these surfaces, magnetic field-line trajectories tend to bunch on that part of the magnetic surface closest to the X point of the magnetic island. Because of this preferential bunching, the stabilizing effect of field-line bending due to magnetic shear can be reduced. Eigenfunctions localized in helical angle near the X point and in poloidal angle on the bad curvature side of the tokamak are more susceptible to ballooning instability than are modes in corresponding equilibria without the magnetic island. For a slowly growing island, a growing number of flux surfaces located near the separatrix become ballooning unstable. Secondary ballooning instabilities may play a part in the crash phase of sawteeth or macroscopic island dynamics.
- OSTI ID:
- 7250450
- Journal Information:
- Physics of Fluids B; (United States), Journal Name: Physics of Fluids B; (United States) Vol. 4:10; ISSN 0899-8221; ISSN PFBPE
- Country of Publication:
- United States
- Language:
- English
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