A study of mode conversion in an oxygen–hydrogen plasma

Linear mode conversion is considered between the ion-cyclotron and magnetosonic branches in a multispecies plasma with parallel magnetic field gradients. The results are interpreted in terms of ion conic heating. The mode-conversion coefficients are solved using perturbation theory, a phase integral approach, and saddle-point theory. These results are compared with numerical calculations. The coefficients thus obtained demonstrate that substantial coupling occurs between the four propagating modes, and a definite absorption occurs. Such absorption corresponds to ion heating and is, under realistic circumstances, sufficient to explain the outflow and heating of ionospheric oxygen.