RF-breakdown in ionosphere by two-frequencies radiation

The HF-breakdown in ionosphere by electric fields of two electromagnetic waves with close frequencies is studied. The essence of this type of discharge concludes in the following. Under the action of the ponderomotive force caused by the fields of two electromagnetic waves, the electrons gain the energy ε_p that is compares to the ionization energy of the gas ε_p~ε _i. This process is faster than direct ionization in the field of separate waves. Consequently the power of the HF source is essentially decreasing. As a result of this breakdown mechanism the plasma is produced of density needed for resonant excitation of plasma wave at parametric three-waves interaction. In the field of the plasma wave the essential acceleration of the breakdown process occurs. It is explained by the fact that the threshold field lowers with frequency decreasing linearly and maximum value of the plasma wave field that is saturated at nonlinear three-waves interaction stage is proportional to the squared root of frequency. Hence, if plasma frequency is more less comparatively to wave frequencies the ionization of the gas will occur in the plasma wave field even at the amplitudes of electromagnetic waves less the threshold breakdown value. The maximum value of plasma waves and growth rate of breakdown are found for the given power of two electromagnetic waves. Some experimental examples are represented on beat-wave excitation of plasma wave and breakdown in ionosphere. It is considered the plasma wake field by using high power short electromagnetic pulse or succession such pulses