Ratchet effect in the inverse turbulent cascade

We present a statistical analysis of the inverse cascade of two-dimensional turbulence in terms of screened vortices in the sense of Landau quasi particles. We emphasize that the effective behaviour of two screened vortices involves an interaction which favours the cluster formation of like-signed vortices. This interaction is of stochastic nature and allows one to consider the turbulent transport in the inverse cascade as a kind of ratchet process.