ALGEBRAIC INSTABILITY OF HOLLOW ELECTRON COLUMNS AND CYLINDRICAL VORTICES

An axisymmetric, amgnetically confined electron column, in which the E×B rotation frequency is not a monotone function of radius, is linearly unstable to two-dimensional, electrostatic disturbances with azimuthal mode number l=1. The perturbation density is asymptotically proportional to t and may be described as a shift of the core of the column. A particle-in-cell simulation indicates that harmonics grow rapidly and that there are secondary instabilities. An identical instability arises in hollow circular vortex columns in an inviscid, incompressible neutral fluid. © 1990 The American Physical Society.