Theoretical studies of plasma wave coupling: A new approach

New numerical and analytical methods are applied to wave coupling in inhomogeneous plasma. It is found that the X-mode feeds energy into the upper hybrid resonance at plasma inhomogeneities oriented perpendicular to the ambient magnetic field. The results are consistent with previous studies using other methods. When a finite pressure is introduced, the upper hybrid waves are no longer stationary and start propagating. They can form cavity modes and emit a small fraction of O (or X) waves. Limitations of the present study are the neglect of collisions and plasma pressure effects which might limit the growth of the upper hybrid waves; furthermore, this study concentrates on the case for which the density gradient is perpendicular to the magnetic field, a condition that is valid near the equator.