Abstract
The backscattering of an intense electromagnetic wave, propagating in the ordinary mode along a number density gradient and perpendicular to a uniform static magnetic field, is investigated. The scatterer wave is from the low-frequency branch of the extraordinary mode which becomes ion acoustic in the limit of vanishing magnetic field. A formula is derived for the threshold intensity of the pump wave associated with the parametric instability. The effect of the static magnetic field on the instability in an inhomogeneous plasma is studied numerically and compared with the case of a homogeneous plasma.