Representation of ideal magnetohydrodynamic modes
- Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)
One of the most fundamental properties of ideal magnetohydrodynamics is the condition that plasma motion cannot change magnetic topology. The conventional representation of ideal magnetohydrodynamic modes by perturbing a toroidal equilibrium field through {delta}B(vector sign)={nabla} Multiplication-Sign ({xi}(vector sign) Multiplication-Sign B(vector sign)) ensures that {delta}B(vector sign){center_dot}{nabla}{psi}=0 at a resonance, with {psi} labelling an equilibrium flux surface. Also useful for the analysis of guiding center orbits in a perturbed field is the representation {delta}B(vector sign)={nabla} Multiplication-Sign {alpha}B(vector sign). These two representations are equivalent, but the vanishing of {delta}B(vector sign){center_dot}{nabla}{psi} at a resonance is necessary but not sufficient for the preservation of field line topology, and a indiscriminate use of either perturbation in fact destroys the original equilibrium flux topology. It is necessary to find the perturbed field to all orders in {xi}(vector sign) to conserve the original topology. The effect of using linearized perturbations on stability and growth rate calculations is discussed.
- OSTI ID:
- 22113420
- Journal Information:
- Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 2 Vol. 20; ISSN PHPAEN; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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