Mode conversion and electron damping of the fast Alfvén wave in a tokamak at the ion–ion hybrid frequency

Abstract

Mode conversion of the fast Alfvén wave (FAW) at the ion-hybrid frequency in the ion cyclotron range of frequencies (ICRF) is studied in the presence of ion cyclotron absorption and direct electron damping in a tokamak plasma. The usual Budden model is extended to include the effect of electron damping and of the high-field-side cutoff, and is solved analytically and numerically. The mode-conversion efficiency is given as a function of the Budden transmission coefficient and of a phase integral, which describes interference between the incoming and outgoing waves. In incidence from the low-field side, a discrete spectrum of phases exists for which complete absorption (i.e., combined mode conversion and direct electron damping) of the FAW for a single transit of the resonance region can be achieved. This permits efficient electron heating and/or current drive via mode conversion of FAWs.

Excitation, propagation, and damping of electron Bernstein waves in tokamaks

“…10, a differential equation is obtained that is identical in form to that found, and solved, for the conversion of fast Alfvén waves to ionBernstein waves near the ion-ion hybrid resonance. 9,10 Carrying over our results from Ref. 10, we find the power mode conversion coefficient is…”

“…This triplet of cutoff-resonance-cutoff is similar to that encountered in the mode conversion of fast Alfvén waves to ion-Bernstein waves at the ion-ion hybrid resonance . 9,10 In such a triplet resonator, one can, in principle, obtain complete mode conversion of the incident power to EBW. The local dispersion relation (6) is not valid for describing the propagation of waves through the cutoffs and resonances.…”

“…This triplet of cutoff-resonance-cutoff is similar to that encountered in the mode conversion of the fast Alfvén waves to the ionBernstein waves at the ion-ion hybrid resonance in plasmas with at least two ion species of different charge-to-mass ratios. 9,10 In this paper we make use of the theory and the results obtained in Ref. 10 to study the X-B mode conversion.…”

Tunneling and mode conversion of fast magnetosonic waves in the magnetospheres of Earth and Mercury

“…If the transmitted FW undergoes additional wave reflection, once a right-hand polarized R-cutoff (ǫ R = n 2 ) or a supplementary MC layer is present in a plasma, the resulting reflection and mode conversion coefficients depend on the constructive/destructive interference between the partially reflected fast waves (Majeski et al 1994;Fuchs et al 1995;Ram et al 1996;Kazakov et al 2010;Kim et al 2011). For the cutoff-resonancecutoff triplet (see Fig.…”

“…For the cutoff-resonancecutoff triplet (see Fig. 1(b)), an accurate analytical expression for the conversion efficiency was derived by Fuchs et al (1995) and Ram et al (1996). It is given by…”