Excitation of whistler modes in ionospheric plasma by an artificially injected electron beam

It is shown that the structure of whistler radiation produced by the artificial injection of an electron beam into the ionosphere can be estimated from the spectral characteristics and radiation pattern of the whistler modes. The dependence of instability increments on the propagation direction of whistler modes is determined for two theoretical beam models. A comparison with experimental data shows that the electron motion of a real beam is semihelical.