Gg. Borg, DIRECT ANTENNA EXCITATION OF THE SHEAR ALFVEN-WAVE AT FINITE FREQUENCY IN THE BOUNDARY OF A FUSION PLASMA, Journal of Plasma Physics, 59, 1998, pp. 151-168
The problem of direct excitation of the shear Alfven wave by antennas
in the boundary of a fusion plasma is considered. In the plasma scrape
-off layer the physics of this wave is determined by finite electron i
nertia. Expressions for the wave electric and magnetic field are deriv
ed without any assumption on the smallness of the ratio of frequency t
o ion cyclotron frequency. It is shown that the shear Alfven wave prop
agates as a guided beam along the steady magnetic field over a wide ra
nge of frequencies below the ion cyclotron frequency, and is predomina
ntly excited by current elements parallel to the steady magnetic field
. A simple transmission-line analogy suggests that guidance of the Alf
ven wave is also expected in the presence of strong plasma inhomogenei
ty.