A CLASS OF COHERENT VORTEX STRUCTURES IN ROTATING NONNEUTRAL PLASMA

A class of nonaxisymmetric (partial derivative/partial derivative thet a not-equal 0) rotating equilibria is investigated theoretically for s trongly magnetized, low-density (omega(pe)2/omega(ce)2 much less than 1) pure electron plasma confined radially by a uniform axial magnetic field B0e(z) between concentric, perfectly conducting, cylindrical wal ls located at radii r = r(w) and r = r(I) < r(w). The analysis is base d on a nonrelativistic, guiding-center model in the cold-fluid limit t hat treats the electrons as a massless fluid (m(e) --> 0) with E X B f low velocity V(e) = -(c/B0)delphi X e(z). Assuming two-dimensional spa tial variations (partial derivative/partial derivative z = 0), the con tinuity-Poisson equations are analyzed for rotating coherent structure s that are stationary (time independent) in a frame of reference rotat ing with angular velocity omega(r) = const about the cylinder axis (r = 0). The equilibrium Poisson equation del2psi = -4pie2n(e)(psi) + 2om ega(r)eB0/c is solved exactly for the particular case where the electr on density n(e)(psi) is a linear function of the streamfunction psi = -ephi + omega(r)(eB0/2c)r2, and the plasma fills the region between th e conducting walls, with n(e) = 0 at r = r(I) and r = r(w). It is foun d that this class of rotating equilibria can exhibit large-amplitude, nonaxisymmetric, vortex structures characterized by strong azimuthal d ensity bunching and circulating electron flow within the density bunch es. Nonlinear stability properties are investigated using the Lyapunov method, and the vortex equilibria with azimuthal mode number l = 1 ar e shown to be stable.