Growth of a ring ripple on a Gaussian electromagnetic beam in a plasma with relativistic - ponderomotive nonlinearity

Abstract

AbstractThis paper presents a theoretical model for the propagation/growth of a ring ripple, on a Gaussian electromagnetic beam, propagating in plasma with dominant relativistic-ponderomotive nonlinearity. A paraxial like approach has been invoked to understand the nature of propagation of the ring ripple like instability; in this approach, all the relevant parameters correspond to a narrow range around the irradiance maximum of the ring ripple. The dielectric function is determined by the composite (Gaussian and ripple) electric field profile of the beam. Thus, a unique dielectric function for the beam propagation and a radial field sensitive diffraction term, appropriate to the vicinity of the maximum of the irradiance distribution of the ring ripple has been taken into account. The effect of different parameters on the critical curves has been highlighted and the variation of the beam width parameter with the distance of propagation has been obtained for the three typical cases viz of steady divergence, oscillatory divergence and self-focusing of the ripple.