Dynamics of excitation of backward waves in long inhomogeneous systems

The spatio-temporal dynamics of excitation of a long backward-wave oscillator with a profiled resonant parameter is studied in detail. It is shown that the transition to multifrequency regimes of the rf generation occurs due to splitting the long oscillator into several shorter single-frequency oscillators with different eigenfrequencies. This fact can be useful, in particular, for an explanation of the dynamics of the intense cyclotron radiation, which is detected escaping from Earth in the kilometric wavelength range