Anomalous Bremsstrahlung in Partially Ionized Plasmas

Abstract

The anomalous bremsstrahlung from partially ionized plasmas is observed in the absence as well as in the presence of the magnetic field when the detecting frequency f is smaller than a critical frequency f_crit, which is somewhat smaller than the collision frequency of plasma electrons; on the other hand, the anomalous cyclotron emission described previously appears when f exceeds f_crit. The experimentally observed characteristics of the former emission are very similar to those of the latter, except for their dependence on the magnetic field and their frequency ranges.
The theoretical considerations suggest that the effect of negative absorption due to the stimulated bremsstrahlung may occur in plasmas. It is shown that we can interpret the anomalous bremsstrahlung as a phenomenon resulting from this effect.