CONDITIONS OF OBSERVATION OF WHISTLER EMISSIONS IN-SPACE

The peculiarities of whistler wave fields spontaneously radiated by el ectron beams artificially injected into the Earth's ionosphere are dis cussed. The conditions of registration of the whistler wave packets by a remote on board VLF receiver have been analyzed; they depend on mut ual disposition of the electron gun and the VLF receiver as well as on the pitch angle of the injected electrons. It is shown that the inter nal frequency width of the whistler Signal, connected with the ray rep resentation of a wave field, depends on the distance between the emitt ing region of the beam and the receiver and determines the lowest band width of the VLF receiver in use. It is found that near the double pol e singularity at the Gendrin's velocity the energy loss of a single el ectron increases by a factor of the order of ratio of the background e lectron plasma frequency to the electron gyrofrequency. The estimation s for the coherence length of the beam and the ratio of coherent to in coherent level of radiated whistler amplitude are also presented. The theoretical analysis of the whistler wave field near the beam front ha s revealed crucial differences between the registration pattern of hig h-frequency and whistler frequency emissions in active experiments sim ilar to ARAKS [1] and APEX [2-3].