Ti. Woodward et Jf. Mckenzie, STATIONARY MHD WAVES MODIFIED BY HALL CURRENT COUPLING .1. COLD COMPRESSIBLE FLOW, Planetary and space science, 42(6), 1994, pp. 463-479
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.