Bifurcated states of a rotating tokamak plasma in the presence of a static error- eld
نویسنده
چکیده
The bifurcated states of a rotating tokamak plasma in the presence of a static, resonant, erroreld are found to be strongly analogous to the bifurcated states of a conventional induction motor. The two plasma states are the \unreconnected" state, in which the plasma rotates and erroreld driven magnetic reconnection is suppressed, and the \fully reconnected" state, in which the plasma rotation at the rational surface is arrested and driven magnetic reconnection proceeds without hindrance. The response regime of a rotating tokamak plasma in the vicinity of the rational surface to a static, resonant, erroreld is determined by three parameters: the normalized plasma viscosity, P , the normalized plasma rotation, Q0, and the normalized plasma resistivity, R. There are eleven distinguishable response regimes. The extents of these regimes are calculated in P -Q0-R space. In addition, an expression for the critical erroreld amplitude required to trigger a bifurcation from the \unreconnected" to the \fully reconnected" state is obtained in each regime. The appropriate response regime for low density, ohmically heated, tokamak plasmas is found to be the nonlinear constantregime for small tokamaks, and the linear constantregime for large tokamaks. The critical erroreld amplitude required to trigger erroreld driven magnetic reconnection in such plasmas is found to be a rapidly decreasing function of machine size, indicating that particular care may be needed to be taken to reduce resonant errorelds in a reactor-sized tokamak.
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