Excitation and propagation of lower-hybrid waves in a bounded, inhomogeneous plasma

Abstract

The excitation and propagation of lower‐hybrid waves in an inhomogeneous, cylindrical plasma is studied theoretically for finite‐length electrostatic sources. The boundary‐value problem for the electrostatic potential in a cold, inhomogeneous plasma is solved numerically as a superposition of the radial eigenmodes excited by a finite‐length source. Radial eigenmodes are found numerically by an algorithm which includes the case where the lower‐hybrid resonance layer occurs in the plasma. The eigenmode superposition is carried out for several phased‐ring sources. The plasma response is found to be composed of resonance‐cone surfaces along which the potential is a maximum. When the resonance layer does not occur in the plasma, the resonance‐cone surfaces reflect from the column axis and at the plasma boundary. For the case when the resonance layer does occur, the resonance‐cone surfaces become asymptotic to the resonance layer and do not penetrate to the center. The presence of damping causes the resonance‐cone singularities to dissolve axially leaving the lowest‐order radial mode excited by the source