Consequences of nongyrotropy in magnetohydrodynamics

It is assumed in the magnetohydrodynamic set of equations that a plasma is both isotropic and gyrotropic at any instant of time. However, this cannot be always justified for applications in space plasmas which are essentially collisionless. By introducing two relaxation time scales, one for isotropization and another for gyrotropization, we propose a model which describes evolution of the field and the plasma variables, including all the pressure tensor elements. We discuss briefly the linear wave dispersion relation of the system, and then attempt to apply the model to the magnetic reconnection.