Analysis of the effect of external gas flow on helical instabilities of arc plasmas

摘要

The effect of external gas flow on helical instability of arcs is studied by using an analytical method. The magnetohydrodynamic equations in an electrostatic approximation serve as the starting point of the theory. Using a linear time-dependent perturbation theory, the analytic expression that corresponds to the term of a gas flow stabilizing effect is deduced, and the growth rate of the helical instability is given. It is found that in the short wavelength perturbation case, the effect of external gas flow is large, so it is beneficial for stabilizing arcs. However, its effect is very small for intermediate and long wavelength perturbations. At the same time, numerical results show that the stabilizing effect of the flow on helical instability increases with increasing shear viscosity of external gas flow. (C) 2001 American Institute of Physics. [References: 8]