The effect of external magnetic field,current and arc column radius on the arc helical instability
外加磁场、电流及弧柱半径对电弧螺旋不稳定性的影响

The effect of external magnetic field, current and arc column radius on the helical instability is studied by using linear time perturbation theory in this paper. The arc has the effect of gas flow. The stability conditions and the growth rate of the helical instability are given.