Abstract
Based on a two-fluid plasma model where the electron mass and the displacement current are neglected, the eigenmode properties such as the frequency and the compressibility are studied. It is found that these properties strongly depend on the two-fluid parameter kl(i), where k is the wave number of a mode and l(i) is the ion skin depth. Especially it is found that as the two-fluid parameter kl(i) increases beyond unity, the Alfven wave, which is an incompressible mode in the magnetohydrodynamics (MHD) limit, becomes compressible and its phase velocity approaches to the acoustic speed. The slow magnetosonic wave, which is compressible in the MHD limit, becomes incompressible as kl(i) increases. Implications of these results are also discussed. (c) 2005 American Institute of Physics.