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One of the most important effects of pumping the ionospheric plasma by a powerful high frequency electromagnetic wave from the ground is the excitation of filamentary density irregularities. These striations are density depletions which contain localized upper hybrid oscillations. The upper hybrid oscillations radiate Z mode waves that escape from the depletions and can therefore scatter on neighboring depletions, which provides a means for electromagnetic interaction between different striations. The physics of a Z mode wave scattering on a single density depletion is studied analytically in one dimension. At resonance the incident Z mode wave is totally reflected from the irregularity. The treatment of many parallel striations interacting through the Z mode radiation shows that different scattering processes are involved to excite the even and odd modes of the localized upper hybrid oscillations. [ABSTRACT FROM AUTHOR]

The formation of vortex structures in an electron plasma with a sheared flow is investigated. The electron fluid is drifting in a self-electric field generated by an unshielded electron population. This setting is linearly unstable and an instability of diocotron (slipping-stream) type occurs. The time scale of the dynamics is assumed to be much shorter than the ion plasma and ion gyroperiods. Consequently, the ions do not respond to the wave potential and serve only as a neutralizing background. An equation determining the nonlinear evolution of the electrostatic potential in a plane perpendicular to an external magnetic field is derived within the drift approximation. The governing equation is then analyzed for the case with a localized shear in the electron fluid velocity. Possible final states of the diocotron instability are investigated analytically and solutions in the form of a tripolar vortex, a zonal flow, and a vortex street are found. The nonlinear time evolution of the diocotron instability is investigated by solving the governing equation numerically. In particular, the dynamics of nonlinearly saturated states and the formation of such states are discussed. Numerical solutions show a vortex street structure in a saturated state. The relevance of our investigation for space and laboratory plasmas is discussed. [ABSTRACT FROM AUTHOR]

The Faraday rotation in a magnetized electron-positron plasma containing a fraction of ions is investigated by using a multifluid description. It is shown that the Faraday rotation for circularly polarized electromagnetic waves with frequencies much larger than the electron/positron plasma and electron gyrofrequencies is proportional to the ion number density and the magnitude of the ambient magnetic-field strength. The results are relevant for astrophysical observations and diagnostics of laboratory electron-positron-ion magnetoplasmas. [ABSTRACT FROM AUTHOR]

Analytic expressions are presented for conversion of localized lower hybrid oscillations and magnetosonic waves by scattering off a small scale density cavity. The governing equations are solved in slab geometry with wave vectors perpendicular to both the ambient magnetic field and the density gradient associated with density cavity using a scale length separation method. The theory predicts strong excitation of localized lower hybrid oscillations for a set of frequencies between the lower hybrid frequency of the ambient plasma and the minimum lower hybrid frequency inside the cavity. The theory is relevant for the lower hybrid solitary structures observed in space plasmas. [ABSTRACT FROM AUTHOR]

Analytic expressions are presented for the conversion of electromagnetically driven quasi-trapped upper hybrid oscillations (i.e., trapping predicted within electrostatic approximation) and electromagnetic Z mode at a density irregularity in a magnetized plasma. This problem is of importance for the theory of plasma density irregularities excited in the ionosphere during radio wave experiments. The governing equations are solved in a slab geometry using a scale length separation method. The results are valid for arbitrary low resonances of the quasi-trapped field. The theory predicts non-Lorentzian skewed shapes of the resonances for the Z mode radiation. [ABSTRACT FROM AUTHOR]