The paper analyzes low-frequency waves in a plasma model that is made up of two thermally anisotropic magnetohydrodynamic components, by means of wave-front diagrams, a useful tool that has not attracted the desired attention. The wave-front diagrams of the fast propagating suprathermal mode, besides the usual fast, slow, and Alfvén modes, have been plotted for a variety of situations. These diagrams are used to bring out the physical significance of the anisotropic model vis-à-vis the isotropic model. The question of stability that has been completely ignored so far in the plasma models based on two magnetohydrodynamic components has also been addressed. Analogues of the firehose and mirror instabilities, which are supported by this model, are examined. Their comparison with single-component anisotropic plasma results suggests the possibility of suppressing the mirror instability.

Low frequency plane waves supported by a medium containing a thermal plasma of isotropic pressure and a suprathermal collisionless plasma having anisotropic pressure are investigated. The usual Alfvén, slow and fast modes of isotropic pressure magnetohydrodynamics persist. In addition, a suprathermal mode appears which displays a rich variety of behavior due to an additional degree of freedom compared to the analogous mode when both the plasma components are described by collision-dominated magnetohydrodynamics. Since these modes are significant in a number of situations, they are extensively investigated by computing their phase speeds for wide-ranging numerical parameters.

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The paper bridges the need for a theoretical formulation for the ponderomotive force, which is necessary for laboratory regimes where plasmas are thermally anisotropic. The calculations are based on a closed set of moment equations obtained from the Vlasov equation, under the assumption of negligible heat flow, for an arbitrary strength of the external magnetic field. The formulation also results in the inclusion of the finite Larmor radius effect, besides pointing out the limitations in the Chew, Goldberger, and Low [Proc. R. Soc. London, Ser. A 236, 112 (1956)] equations which have been frequently used to describe an anisotropic temperature plasma.

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