Toroidal coupling of ideal magnetohydrodynamic instabilities in tokamak plasmas
- Departments of Nuclear Engineering and Engineering Physics and Physics, University of Wisconsin, Madison, Wisconsin 53706-1687 (United States)
- UKAEA Government Division, Fusion (Euratom/UKAEA Fusion Association), Culham, Abingdon, Oxfordshire, OX14 3DB (United Kingdom)
A theoretical framework is developed to describe the ideal magnetohydrodynamic (MHD) stability properties of axisymmetric toroidal plasmas. The mode structure is described by a set of poloidal harmonics in configuration space. The energy functional, {delta}{ital W}, is then determined by a set of matrix elements that are computed from the interaction integrals between these harmonics. In particular, the formalism may be used to study the stability of finite-{ital n} ballooning modes. Using for illustration the {ital s}-{alpha} equilibrium, salient features of the {ital n}{sq_bullet}{infinity} stability boundary can be deduced from an appropriate choice of test function for these harmonics. The analysis can be extended to include the toroidal coupling of a free-boundary kink eigenfunction to the finite-{ital n} ideal ballooning mode. A unified stability condition is derived that describes the external kink mode, a finite-{ital n} ballooning mode, and their interaction. The interaction term plays a destabilizing role that lowers the instability threshold of the toroidally coupled mode. These modes may play a role in understanding plasma edge phenomena, L{endash}H physics and edge localized modes (ELMs). {copyright} {ital 1996 American Institute of Physics.}
- DOE Contract Number:
- FG02-86ER53218
- OSTI ID:
- 278491
- Journal Information:
- Physics of Plasmas, Vol. 3, Issue 2; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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