On the efficiency of ion Bernstein wave launching

To investigate the efficiency of ion Bernstein wave (IBW) excitation in the scrape-off region by mode conversion of externally launched slow cold plasma waves (SWs), the integral wave equation of a strongly dispersive plane stratified plasma is solved with the help of a Galerkin finite element method. Numerical solutions show that conversion is complete if local damping can be avoided. Parasitic loss channels, namely ion cyclotron damping of the IBWs and electron Landau damping of the SWs and of the IBWs are quantitatively investigated. A relaxation time analysis of collisional damping shows that even a slight anomalous increase of the effective collision frequencies can cause dissipation of a nan-negligible fraction of the launched power. Power deposition profiles are calculated on the basis of a local power balance, valid to all orders of the ratio of gyroradius to wavelength.