Energy anisotropy instabilities in high-beta plasmas: A comparison of various kinetic and fluid descriptions

The Vlasov-fluid model is employed to study linear perturbations of a particular class of magnetized, infinite, homogeneous equilibria. The dispersion properties of waves and anisotropy driven instabilities with frequencies at or below the ion cyclotron frequency are used to compare and contrast the Vlasov-fluid model with other well-known models of a high-beta plasma. Although the various models differ widely in physical content and in the manner in which the dispersion equation is derived, the results obtained from any one of them agree with appropriate limits of all the others. The results illuminate the nature of the anisotropy driven fluid-like instabilities and illustrate their connection to kinetic descriptions that include dispersion due to finite gyroradius effects. For the simple equilibria that have been considered, no reason has been found not to regard the Vlasov-fluid model as an acceptable model of a high-beta plasma