Hybrid magnetohydrodynamic-kinetic electron closure methods and shear Alfven waves in nonuniform plasmas

Two hybrid magnetohydrodynamic-kinetic electron models of shear Alfven waves with different,closure schemes involving the assumption of quasineutrality are compared. One method assumes quasineutrality directly while the other allows for a nonzero del - (->)(j) that produces a correcting electric field. The interpretation of the different closure schemes is discussed and the two methods are shown to yield consistent results for both the cases of a constant and Variable density along the field line. In the variable density case the hybrid system with and without a shear Alfven wave perturbation is also contrasted. In the, latter case, static parallel electric fields that increased with the plasma temperature were generated to support the density gradients. When the system was perturbed, a time dependent parallel electric field contribution oscillated around the static field structure needed to support the profile. Landau damping effects were also investigated and the energy invariant for the systems derived. (c) 2005 American Institute of Physics.