NONLINEAR SOLITARY WAVE IN THE IONOSPHERIC E-REGION

A nonlinear wave equation for a solitary one-dimensional inhomogeneity is studied. It is similar to the diffusion equation with the diffusio n coefficient depending on the phase velocity. The phase velocity depe nds, in turn, on the electron density. A weak inhomogeneity moves with the velocity close to that of the electric drift. If this velocity ex ceeds the ion acoustic speed the effective diffusion is negative, and the inhomogeneity grows and contracts. The velocity of the growing inh omogeneity becomes smaller. It absorbs weaker and faster moving inhomo geneities from the back side. In a stationary regime, the ionosphere w ill be filled with rare but strong inhomogeneities with sharp back sid es. (C) 1996 Elsevier Science Ltd