First Observations of Strong Anomalous Absorption of Microwave Beam of Ordinary Polarization in Plasma Filament

Model experiments at the Granit linear facility revealed anomalous absorption of microwave power of a pump ordinary wave in a plasma filament. This absorption is observed under conditions when there were no linear mechanisms in the plasma volume that could explain this phenomenon. Theoretical analysis shows that this anomalous absorption may be a consequence of the excitation of low-threshold parametric decay instability of the pump ordinary wave. The instability development results in the excitation of daughter upper-hybrid and electron plasma waves localized in the central part of the plasma filament.