Deformation and striation of plasma clouds in the ionosphere: 2. Numerical simulation of a nonlinear two-dimensional model

We present and solve numerically a coupled pair of nonlinear partial differential equations that describe the self-consistent evolution transverse to the magnetic field of plasma clouds artificially formed in the ionosphere. This model assumes that the height-integrated Pedersen conductivity of the cloud dominates the ionospheric contribution and that the cloud is sufficiently high so that κi = Ωi/νin ≫ 1. Several initial states are examined, and many features of field observations of recent barium releases are obtained: early time elongations in the E × B direction (due to convection and not diffusion), backside steepening, slower frontside motion, and striations or development of fingerlike sheets of plasma structure on the backside with a long-time tendency to fission into rods. The onset time for striations is a complicated function of the shape of the cloud, the intensity, the structure, and the location of the initial perturbation and the underlying dissipation.