Plasma stability in a dipole magnetic field

The MHD and kinetic stability of an axially symmetric plasma, confined by a poloidal magnetic field with closed lines, is considered. In such a system the stabilizing effects of plasma compression and magnetic field compression counteract the unfavorable field line curvature and can stabilize pressure gradient driven magnetohydrodynamic modes provided the pressure gradient is not too steep. Isotropic pressure, ideal MHD stability is studied first and a general interchange stability condition and an integro-differential eigenmode equation for ballooning modes are derived, using the MHD energy principle. The existence of plasma equilibria which are both interchange and ballooning stable for arbitrarily large beta = plasma pressure / magnetic pressure, is demonstrated. The MHD analysis is then generalized to the anisotropic plasma pressure case. Using the Kruskal-Oberman form of the energy principle, and a Schwarz inequality, to bound the complicated kinetic compression term from below by a simpler fluid expression, a general anisotropic pressure interchange stability condition, and a ballooning equation, are derived. These reduce to the usual ideal MHD forms in the isotropic limit. It is typically found that the beta limit for ballooning modes is at or just below that for either the mirror mode or the firehose.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2001

Author dc:creator

• Simakov, Andrei N., 1974-

Advisor dc:contributor.advisor

• Peter J. Catto and Miklos Porkolab.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/60756

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/60756