On the linear stage of thermal parametric instabilities in the ionosphere excited by HF pumping near electron gyroharmonics

• Published in: Advances in space research Vol. 38; no. 11; pp. 2527 - 2532
• Main Authors: Norin, L., Grach, S.M., Thidé, B.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 2006
• Subjects: Electron gyroharmonics; Fysik; Inhomogeneous inosphere; NATURAL SCIENCES; NATURVETENSKAP; Physics; Thermal parametric instability; Electron gyroharmonics; Thermal parametric instability; Inhomogeneous inosphere
• ISSN: 0273-1177; 1879-1948; 1879-1948
• DOI: 10.1016/j.asr.2004.12.014

Thresholds and growth rates of the thermal parametric instability in the ionosphere were studied taking into account the regular inhomogeneity (altitude dependence) of the plasma density and of the magnetic field strength. A noticeable decrease of the pump wave threshold power and an increase of the growth rate occurs when f 0 approaches the double resonance frequency f d = nf ce( z d) = f UH( z d), z d being the altitude for double resonance. Particularly, the threshold power decreases relative to the non-resonant case by a factor 3–7 at | f 0 − f d( z d)| ≲ 15 kHz for n = 3 and up to a factor 3 for n = 4. The instability growth rate can increase with a factor of 10 3–10 4 relative to the non-resonant case. The decrease of the threshold and increase of the growth rate occur for quite small scales of the striations, l ⊥ ∼ 1 m for n = 3 and l ⊥ ∼ 0.5 m for n = 4.