13 Dec 2006; Mat-Nat Faculty (UiTø), room U1=A228. Wednesday 10:15-12:00

Thierrry Passot (University of Nice, France)

"A FLR-Landau fluid model for the simulation of Alfvén wave cascade and mirror structures".

In space plasmas such as the warm interstellar medium, the solar wind or the terrestrial magnetosheath, magnetic fluctuations display turbulent power law spectra, coherent structures in the form of solitary waves or even collapsing events. In order to understand these phenomena that involve scales of the order smaller than the ion gyroradius and most often much smaller than the mean free path, usual  magnetohydrodynamic equations have to be generalized. I shall present a Landau fluid model that retains pressure anisotropy, a refined description of linear Landau damping and finite Larmor radius corrections. It is based on the linearized Vlasov equation with a gyrokinetic scaling and retains all the fluid nonlinearities up to those involved in the gyrotropic heat flux equations. This model accurately captures the mirror instability and  the dispersion and damping of kinetic Alfven waves up to scales much smaller than the ion inertial length, but also retains large-scale fast magnetosonic waves.

Several tests of the model will be presented. I shall also discuss the dynamics of mirror modes close to threshold.