ROTATIONAL EFFECTS ON THE M=1 MAGNETOHYDRODYNAMIC INSTABILITY IN SPHEROMAKS

The effect of rotation on the magnetohydrodynamic stability of m = 1 m odes in spheromaks is calculated to reveal a threshold for rotational instability at OMEGAtau(A) almost-equal-to 0.2, where OMEGA is the ang ular rotation frequency and tau(A) is the Alfven transit time. This re sult may explain the appearance of m = 1 modes in spheromak experiment s in which the flux conserver aspect ratio L/R lies well below the thr eshold for the tilt instability (m=n=1). For flux conservers with aspe ct ratios above the tilt instability threshold, rotational instability dominates when OMEGAtau(A) exceeds the rotational threshold.