EXPANSION AND NONLINEAR RELAXATION OF A STRONGLY MAGNETIZED NONNEUTRAL ELECTRON-PLASMA DUE TO ELASTIC COLLISIONS WITH BACKGROUND NEUTRAL GAS

The expansion and nonlinear relaxation of a non-neutral electron plasm a due to elastic collisions with constant collision frequency nu(en) b etween the plasma electrons and a low-density background neutral gas a re investigated theoretically. The model treats the electrons as a str ongly magnetized fluid (omega(pe)(2)/omega(ce)(2) much less than 1) wi th isothermal temperature T=const immersed in a uniform magnetic field B0 (e) over cap(z); The model also assumes an axisymmetric plasma col umn (partial derivative/partial derivative theta=0) with negligible ax ial variation (partial derivative/partial derivative(z)=O). Introducin g the scaled radial coordinate rho=r/r(0)(t), and the density profile shape function eta(rho,t) = [2 pi r(0)(2)(t)/N]n(r,t), a diffusion equ ation is derived that describes the nonlinear evolution and relaxation of eta(rho,t) in response to electron collisions with the neutral gas . A very important consequence of the present analysis is that electro n-neutral collisions (nu(en)not equal 0) cause the electron density pr ofile to relax to a (slowly expanding) quasiequilibrium state with ide ntical profile shape eta(eq)(rho) to that which would be produced by r elaxation to thermal equilibrium by electron-electron collisions in th e absence of background neutral gas (nu(en)=0). (C) 1996 American Inst itute of Physics.