Internal Plasma Resonance of Positive Column near Electron Cyclotron Harmonic Frequencies

A series of subsidiary resonance peaks observed near the electron cyclotron harmonics is studied by the measurements of microwave radiation from a positive column in a magnetic field. When the positive column is irradiated by an external microwave, an intensity of subsidiary resonance peaks increases extremely and also a number of their peaks increases. Further, their dispersion curves displace toward a higher magnetic field and toward a higher electron density, compared with those when there is no external microwave power. The experimentally observed behaviour of the peaks can be explained that a series of subsidiary resonance peaks is resulted from the internal plasma resonance due to the standing plasma waves within the propagating region of the plasma column.