Large time asymptotics of nonlinear drift-diffusion systems with Poisson coupling

We study the asymptotic behavior as t --> +infinity of a system of densities of charged particles satisfying nonlinear drift-diffusion equations coupled by a damped Poisson equation for the drift-potential. In plasma physics applications the damping is caused by a spatio-temporal rescaling of an "unconfined" problem, which introduces a harmonic external potential of confinement. We present formal calculations (valid for smooth solutions) which extend the results known in the linear diffusion case to nonlinear diffusion of e.g. Fermi-Dirac or fast diffusion/porous media type.