Growth of a Gaussian ripple on a uniform-plane wave front in plasmas

This paper presents an investigation of the growth of a Guassian ripple on a uniform-plane electromagnetic wave front in plasmas. The redistribution of electron density in a plasma because of nonuniform intensity distribution along an electromagnetic wave front gives rise to a nonlinear dependence of the effective dielectric constant on the intensity. The redistribution in collisionless plasmas takes place because of ponderomotive force; this is also true in collisional plasmas for periods less than the energy relaxation time τε. The redistribution in collisional plasmas for periods greater than the energy relaxation time τε is on account of the nonuniform heating of electrons along the wave front. This nonlinearity in the effective dielectric constant makes a ripple of a given radius to self-focus, when the initial power of the ripple (P) is between two critical powers (Pcr1