On the penetration of upper hybrid waves into a plasma depletion Original Research Article

Upper hybrid waves propagating into a plasma depletion strictly across magnetic field lines meet a turning point at which the wave group velocity tends to zero. This provides a limitation on the depth of upper hybrid wave penetration into a depletion. The maximum depth depends essentially on the sign and magnitude of the difference between the wave frequency and the closest harmonic of the electron cyclotron frequency. The role of this effect in ionospheric modification as well as in laboratory experiments is discussed.