On origin of outshifted plasma lines during HF modification experiments

Abstract

Abstract.Outshifted I)lasma lines, observed during injections of intense HF ra(tiowaves into the io•osphere, are due to scattering on Langlnuir waves with an unusually large spectral widi, h shifted above the injected frequency. Incoherent scatter radar observations reveal that these waves sometimes are located at altitudes exceeding by several kilolneters the altitude of the reflection layer of the ordinary HF wave, titus making an explanation in terlns of the so-called "free mode" problematic. We show that these ol•servations may be consistently described by the creation, (lue to the ponderomotive force, of density depletions in the Airy pattern of the Z i•to(le. Tlte geileration of Langmuir plasmons by accelerated suprathermal electrons i•tside the depletions causes the wide spectral width of these plasma line features and their Inean frequency shift.

On the onset of HF‐induced airglow at HAARP

“…Its threshold field is E 0 uh ∼ 0.08 V/m if the matching conditions are met at x uh = k uh 2 r e 2 < 1, where r e is the thermal electron gyroradius and k uh is the uh ‐wave vector. Landau damping of short‐scale lower hybrid waves raises the threshold otherwise [ Mishin et al , 1997]. For f 0 = 7.8 (6.8) MHz and θ ≃ 14.5°, the matching conditions at the reflection height H θ are easily satisfied for x uh ≃ 0.3 (≃0.15).…”

Modification of the High-Latitude Ionospheric F Region By High-Power HF Radio Waves at Frequencies Near the fifth and Sixth Electron Gyroharmonics

“…На шестой гармонике гирорезонансов подавление МИИН с теми же пространственными масштабами практически не происходит. на высотах вблизи отражения мощной КВ радиоволны от ионосферы [21,22,23,24]. При возбуждении PDI (parametric decay instability) происходит трехволновой параметрический распад высокочастотной электромагнитной волны накачки на более слабую высокочастотную волну Ленгмюра (электростатические плазменные колебания) и низкочастотную ионно-акустическую волну [1, 22,28].…”

HF-induced airglow at magnetic zenith: theoretical considerations

“…Here, r e is the thermal electron gyroradius and k uh is the uh-wave vector. Otherwise, Landau damping of short-scale lower hybrid waves raises the threshold value (Mishin et al, 1997). The rise time of the (primary) uh-wave is τ uh ∼1-3 ms.…”