STATIONARY MHD WAVES MODIFIED BY HALL CURRENT COUPLING .1. COLD COMPRESSIBLE FLOW

The stationary wave system generated by the inductive interaction betw een a conducting body and a magnetized plasma in relative motion is im portant in such space plasma systems as the Io-Jupiter interaction and tethered satellite systems in the ionosphere. This paper generalizes previous work by the authors on MHD wave perturbations to include Hall current effects, which couples the three MHD modes in a dispersive as well as an anisotropic wave system. There is no longer purely one-dim ensional propagation of any perturbation and consequently the wave mod es suffer quasi-spherical and conical attenuation. The special cases o f cold compressible (part I) and incompressible plasmas (part II) are discussed in detail. In the cold plasma case two wave modes appear: na mely the Alfven ion-cyclotron mode which propagates quasi-one-dimensio nally along the background magnetic field and suffers a resonance at t he proton gyrofrequency above which it is evanescent; and the quasi-is otropic fast Alfven mode which continues to propagate above the proton gyrofrequency. The stationary wavecrest surfaces generated in a perpe ndicular flow reflect the propagation characteristics of the particula r mode to which they correspond. Only the fast Alfven mode experiences the effect of a critical Mach number (at Alfven Mach number M = 1) be low which the associated stationary wavecrest surface disappears and t he mode becomes evanescent. Furthermore as a consequence of the disper sive nature of the system the wavecrests do not represent generalized cones as in the MHD case, and are found downstream of and disconnected from the source. The magnetic pressure and parallel current disturban ces exhibit characteristics of both wave modes present, while the elec tric potential perturbations display in addition the influence of an A lfven-like potential operator together with an ''intrinsic'' potential which arises as a result of including Hall current effects in the sys tem. In very sub-Alfvenic flows in a cold plasma the parallel current perturbation is largely of Alfven ion-cyclotron mode character, while the dominant contribution to the magnetic pressure disturbance is from the evanescent fast Alfven mode. The concomitant electric potential i s predominantly determined by the intrinsic term.