Selective destabilization of ion cyclotron modes

Observations of the current-driven electrostatic ion cyclotron instability, both at Tsub(e)/Tsub(i) = 1 and Tsub(e)/Tsub(i)>>1, show that as the normalized wave number, ksub(perpendicular to) rhosub(i) is varied, different modes (m = 1,2,3...) become successively the most unstable mode. The calculated values of ksub(perpendicular to)rhosub(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. (author)