Fluid description of kinetic modes

The classical kinetic modes, such as the Bernstein mode, the loss cone modes, and the Harris dispersion relation are reconstructed from a fluid-like analysis. The analysis begins with a delta function in the equilibrium distribution. By simply calculating the displacement of a single electron exposed to a small signal electric field, the charge perturbation density, and the dispersion relation, immediately follow. The effect of a velocity distribution enters only through a trivial integration of the dispersion relation thus obtained for the monoenergetic plasma. The entire analysis is done in the configuration space. Thus, without explicitly performing the customary integration over the unperturbed orbits in phase space, finite Larmor radius effects to all order have been retained. Possible extensions to nonuniform plasma and to nonuniform magnetic fields are indicated.