Magnetohydrodynamic stability of negative central magnetic shear, high pressure (ebpol@1) toroidal equilibria
نویسنده
چکیده
The magnetohydrodynamic ~MHD! stability of negative central magnetic shear toroidal equilibria with q.2 everywhere and ebpol@1 is investigated. Here, q is the safety factor of the equilibrium magnetic field in a torus with inverse aspect ratio e , and bpol is the ratio of the plasma pressure to the pressure in the poloidal magnetic field. At small ebpol!1, the elimination of the q52 resonant surface in a negative shear equilibrium greatly improves resistive MHD stability as compared to equilibria with a monotonic q-profile containing a q52 resonant surface. However, at large ebpol@1, the reversal of the central magnetic shear and the elimination of the q52 resonant surface does not improve MHD stability. The existence, or non-existence, of rational magnetic surfaces has no impact on MHD stability when ebpol@1. Altering the current profile, and with it the q-profile, does not affect MHD stability when ebpol is no longer small. Stability is not improved by vertical elongation of the plasma in the poloidal plane. The utilization of an external vertical magnetic field to move the magnetic axis in major radius also does not improve MHD stability. © 1997 American Institute of Physics. @S1070-664X~97!04108-6#
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