On parametric instabilities in HF heating of the ionosphere

Abstract

The initial processes excited directly by high-frequency (HF) heating waves include parametric decay instabilities, which decay the HF heating wave to a frequency-downshifted Langmuir/upper hybrid sideband together with an ion acoustic/lower hybrid wave as the decay mode, and oscillating two stream instabilities, which decay the HF heating wave to two oppositely propagating Langmuir/upper hybrid sidebands and purely growing mode/field-aligned density irregularities. These instabilities provide effective channels to convert heating waves to electrostatic plasma waves in the F region of the ionosphere. The following-up parametric instabilities include the cascades of Langmuir pump waves into Langmuir sidebands and ion acoustic waves/lower hybrid waves, and the decay of upper hybrid waves to Langmuir sidebands and ion decay modes, as well as the filamentation of those HF electrostatic waves to generate field-aligned density irregularities. The instability thresholds, growth rates, angular distribution and regions of excitation are determined.

The three-wave coupling coefficients for a cold magnetized plasma

“…We note that the ion contributions dominate the first three terms in (5), whereas the electron contributions are most important for the fourth term in (5). As a result we have a non-zero coupling coefficient C for the particular case of interaction between three Alfvén waves, in contrast to what one obtains from the too simplified textbook MHD equations (Brodin and Stenflo 1988; where C AAA was zero).…”

“…It can also be useful in interpretations of stimulated scattering of electromagnetic waves in space plasmas (e.g. Stenflo 1999;Kuo 2001;2003). In the latter case we refer the reader to a short historical account of stimulated electromagnetic emissions in the ionosphere (Stenflo 2004).…”

Full-scale simulation study of stimulated electromagnetic emissions: The first ten milliseconds

“…The plasma turbulence is usually studied by ground-based radars, while the escaping stimulated electromagnetic emission (SEE) is recorded by ground-based receivers. A number of nonlinear processes have been identified, including three-wave decay of the electromagnetic wave into Langmuir and ion acoustic waves (the so called parametric decay instability), Langmuir turbulence, and the formation of cavitons (Stenflo andShukla 1997, 2000;Kuo 2001Kuo , 2003. The nonlinear interaction between intense radar beams with ion velocity gradients and the Farley-Buneman modes in the Earth's atmosphere have also been considered.…”