A theory for high-frequency electromagnetic sideband generation by two pump waves


  • Z. H. Huang


Sidebands on the high-frequency (HF) waves received from two transmitted waves separated by small frequency intervals were first observed in January 1984 at the Arecibo Observatory (Ganguly and Gordon, 1986). Papadopoulos proposed that the nonlinear mechanism for the HF sideband generation is a parametric decay of a high-frequency radio wave into a low-frequency compressional Alfven wave and a high-freqeuncy sideband (Papadopoulos et al., 1982). In 1984, Fejer proposed another nonlinear mechanism (phase modulation) for the HF sideband generation (Fejer et al., 1985; Huang and Fejer, 1987). A modulation index theory using the WKB approximation is proposed here, showing that the amplitude of the sidebands are related to (1) the incident HF power, (2) the HF frequency, (3) the temperature of the electrons, (4) the scale height of the ionosphere, and (5) the difference frequency of the two HF pump waves.