ENHANCED COUPLING OF THE FAST-WAVE TO ELECTRONS THROUGH MODE CONVERSION TO THE ION HYBRID WAVE

An analysis of ion cyclotron resonance heating in a plasma containing two ion species is given. Particular emphasis is placed on the importa nt case of comparable concentrations of the two species. The propertie s of ion-Bernstein waves in such a plasma are discussed. A summary of the cutoff-resonance (Budden) and cutoff-resonance-cutoff (triplet) co nfigurations is given and an analytic expression obtained for the Budd en transmission coefficient (relevant also to the triplet case), which is valid for any concentration ratio of the two-ion species. A formul a for the damping coefficient of the ion hybrid wave is obtained and a ray tracing code is used to illustrate the absorption of this mode by electrons close to the two-ion hybrid resonance. The reduced, second- order fast wave equation is solved numerically, illustrating the trans ition from strong electron heating through mode conversion at the two- ion hybrid resonance to direct electron damping of the fast wave in a high beta plasma.