Selective destabilization of ion cyclotron modes

Abstract

Observations of the current-driven electrostatic ion cyclotron instability, both at T_e/T_i=1 and T_e/T_i>>1, show that as the normalized wave number, k_{perpendicular to} rho _i is varied, different modes (m=1, 2, 3...) become successively the most unstable mode. The calculated values of k_{perpendicular to} rho _i at which the cross-over from one mode to the next occurs are in reasonable agreement with the observed values provided that the local density gradient is taken into account.