Excitation of an upper hybrid wave by a Gaussian electromagnetic beam in ordinary mode

This paper presents an investigation of the excitation of an upper hybrid wave in a hot collisionless magnetoplasma by a Gaussian EM beamm propagation perpendicular to the static magnetic field and having its electric vector polarized along the direction of the static magnetic field (ordinary mode). On account of the Gaussian intensity distribution of the EM beam the ponderomotive force becomes finite and the electorns are redistributed. The amplitude of the upper hybrid wave, which depends on the background electron concentration, is thus nonlinearly coupled with the EM wave. When the initial power of the EM wave is between the two critical powers P_cr1 and P_cr2 (P_cr1 < P_cr2) self-focusing occurs. On the other hand, for very low powers (P < P_crl) and high powers (P > P_cr2), monotonic and oscillatory defocusing of the EM wave occurs. The dynamics of the excitation of the upper hybrid wave in these different power domains of the pump wave is accordingly modified. Moreover it is seen that the effect of changing the strength of the static magnetic field on the nonlinear coupling, and hence on the dynamics of the excitation of the upper hybrid wave, is significant.