Spectral features of ionospheric plasma waves excited by powerful HF radio waves radiated at frequencies near electron gyroharmonics and F2-layer critical frequency

• Published in: Solnechno-Zemnaya Fizika
• Main Authors: Borisova T. D., Blagoveshchenskaya N. F., Kalishin A. S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: INFRA-M 2023
• Subjects: high-latitude ionosphere; f-region; powerful hf radio wave; langmuir wave; ion-acoustic wave; incoherent scatter; eiscat; Astrophysics; QB460-466; Norway; Tromsø; Langmuir; EISCAT
• Online Access: https://doi.org/10.12737/szf-92202312; https://doaj.org/article/f827a9cea4a34e4899f33753d82da474

We present the result of the studies into characteristics of high-latitude ionospheric F-region longitudinal plasma waves (Langmuir and ion-acoustic), caused by the impact of powerful HF radio waves of ordinary (O-mode) or extraordinary (X-mode) polarization of the EISCAT/Heating facility, Tromsø, Norway. The powerful HF radio waves on October 20, 2012 and February 26, 2013 were emitted in the direction of the magnetic zenith with a step change in the effective radiation power (ERP). The radiation frequency fH of the EISCAT/Heating facility on February 26, 2013 was close to the F2-layer critical frequency foF2 (fH/foF2~1) and exceeded the electron gyroresonance frequency fH>5fce. On October 20, 2012, the conditions fH/foF2~0.85–0.95 and fH<6fce were fulfilled. Analysis of EISCAT measurements of an incoherent scatter radar (ISR) at a frequency of 930 MHz, spatially aligned with the heating facility for radiation conditions ERP<200 MW, has shown that parametric decay instabilities are excited at the ionospheric heights where the pump frequency is close to the plasma Langmuir frequency, fH≈fPL. We have studied peculiarities of excitation of the decay parametric instabilities as a function of height in the ionosphere and pump wave polarization, the ratios between fH and foF2, and also fH and nfce.