Parametric Decay and Mode Conversion upon Laser-Wave Interaction with Plasma in an Inhomogeneous Magnetic Field

Resonance interaction of a laser wave at twice the upper hybrid frequency with plasma in an inhomogeneous magnetic field is analyzed. A linear dependence of the magnetic field on the coordinate along the direction of propagation of the laser pulse and fulfillment of the resonance condition at the center of the plasma layer are assumed. It is demonstrated that the laser wave decays into two upper hybrid plasmons accompanied by excitation of the Bernstein modes under such an interaction. The occurance of an electromagnetic wave at the upper hybrid frequency reflected from the plasma boundary is detected. The conclusion is drawn that the reflected wave is driven upon interaction of the Bernstein modes with the upper hybrid plasmons since the wave disappears in the case of a cold-plasma layer. The dependence of average energy gained by electrons upon development of instability on the gradient of the external magnetic field is investigated.