Nonlinear Interaction of Electromagnetic Radiation with a Weakly-Magnetized Nonuniform Plasma

Abstract

As is well-known, an electromagnetic wave propagating through a magnetized inhomogeneous plasma excites a short-wavelength upper-hybrid wave at the resonant layer in the mode-conversion process. The ponderomotive force associated with the upper-hybrid wave modifies the density profile to generate the upper-hybrid soliton. In the present study, the space-time evolution of the interaction of long-wavelength radiation with a weakly magnetized plasma (ω ²_c ≪ ω ²_p , ω²) is investigated theoretically and experimentally. A simple model is presented which contains the effect of zeroth-order density gradient, external pumping, and self-consistent density changes due to the ponderomotive-force effect. The numerical solution of the initial value problem reveals two stages of the nonlinear process: In the weakly nonlinear regime, the upper-hybrid wave is repeatedly generated and flows down the density gradient because of the density modification and the ion inertia. In the strongly nonlinear regime, the wave is trapped and grows in the density cavity to form the sharply localized soliton. These features are confirmed in the laboratory experiment where the microwave burst is externally radiated from an antenna to a radially inhomogeneous plasma under the axial magnetic field.