Cerenkov radiation and the front structure of a beam injected into the ionosphere

An investigation of the front structure of the beam injected into the ionosphere in conditions corresponding to the “Electron Echo” Experiment (Hendrickson et al., 1971) is presented. It is shown that the front region of the beam is bunched and the Cerenkov radiation of the bunched beam is investigated. An explanation of the maxima of the amplitudes for definite pitch angles, observed in experiments, is given.