ISSN:
1089-7674
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The asymptotic linear response of the plasma to a finite frequency external magnetic perturbation is analyzed by using the reduced magnetohydrodynamics (MHD) resistive equation with antenna boundary conditions. Different regimes are identified depending on the parameter ω/η1/3k2/3, where ω is the difference between the antenna frequency and the rotation frequency at the rational surface normalized to the poloidal Alfvén time, and η is the normalized resistivity (the inverse of the Lundquist number). The solution for ψ (magnetic flux function) at the rational surface that interpolates the known constant-ψ regime, ω(very-much-less-than)η1/3k2/3, and the ideal regime, ω(very-much-greater-than)η1/3k2/3, is found. In the ideal regime the presence of Alfvén resonances prevents reconnection and island formation at the rational surface. The results of recent experiments in the Joint European Torus JET [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)], where the external magnetic field perturbations are produced by the saddle coil system are also presented. These show the presence of a resonant response of the MHD stable plasma when the antenna frequency approaches the rotation frequency of the corresponding rational surface. © 1999 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.873233
Permalink