Linear and nonlinear electrostatic modes in a nonuniform magnetized electron plasma

Linear and nonlinear low-frequency modes in a magnetized electron plasma ar e studied, taking into account a proper description of the equilibrium plas ma state that is inhomogeneous. Assuming a homogeneous magnetic field and s heared plasma flows, flute-like perturbations are studied in the presence o f density and potential gradients. Linear analysis reveals the presence of a streaming instability and depicts conditions for global linear spiral mod e. In the nonlinear domain, a tripolar vortex, which is driven and carried by the flow, is found. Also investigated are the consequences of a magnetic shear as well as nonuniformities along the magnetic field lines, which are shown to be responsible for the possible annulment of the magnetic shear e ffects. Streaming along the lines of the sheared magnetic field is also stu died. A variety of nonlinear structures (viz. global multipolar vortices, l ocal vortex chains, and tripolar vortices) is shown to be the consequence o f the simultaneous action of the parallel and perpendicular flows. (C) 2001 American Institute of Physics.