Propagation of ion-acoustic double layer in an inhomogeneous plasma

Abstract

Using the reductive perturbation technique, the propagation characteristics of ion-acoustic double layer in a spatially inhomogeneous plasma have been investigated. We have derived a modified Korteweg-de Vries (mKdV) equation with varying coefficients for an inhomogeneous plasma with two Maxwellian electron species. The double layer solution of the mKdV equation is discussed in detail. The present analysis shows that the inhomogeneous plasma density n0 does not affect the amplitude of the double layer, ϕm, whereas its width and velocity are found to decrease as it propagates in the higher density region. It is found that the peak compressed (rarefied) ion density, n1m, corresponding to compressive (rarefactive) double layer increases as the double layer moves along the positive density gradient. The relevance of the present theory to the space plasmas is pointed out.