On the stability of cyclotron radiation emitted perpendicularly to a magnetic field

For wave propagation perpendicular to the static magnetic field, it is investigated whether or not the resonant absorbtivity at the cyclotron frequency harmonics can change spin, i.e. turn unstable. The conclusion is that this is possible, but only likely to occur in the extraordinary mode in a plasma where runaway electrons have a sufficiently high perpendicular energy. (author)