November 4, 2011, 12:00 pm - 1:00 pm

November 4, 12:00 pm - 1:00 pm

A new approach in understanding solar wind turbulence: Landau fluid model

Dr. Peter Hunana, NASA GSFC

A so-called FLR-Landau fluid model, which extends the usual MHD by incorporation of linear kinetic effects such as linear Landau damping and finite Larmor radius (FLR) corrections, will be discussed. The first three-dimensional numerical simulations of decaying turbulence will be presented and compared to simulations of compressible Hall-MHD. It will be shown that linear Landau damping is responsible for significant damping of magnetosonic waves. Compressibility of the fluid and parallel energy transfer along the ambient magnetic field are also significantly inhibited when plasma beta is not too small. In contrast with gyrokinetic description, the Landau fluid model allows for development of strong temperature anisotropies and correctly captures the threshold and growth rate of mirror instability, which is often observed in the solar wind. It will be also argued that the large-scale FLR corrections, which are typically used by many authors, fail in presence of strong temperature anisotropies, because they introduce unphysical instabilities.