Joint observations of atmospheric parameter variations by the Fabry-Perot interferometer and the Irkutsk incoherent scatter radar

The work is based on observations carried out within the framework of the scientific and educational intensive course of the Baikal young scientists’ international school on fundamental physics in Irkutsk from September 5 to 10, 2022. The intensive course participants carried out work on unique scientific facilities of ISTP SB RAS: the Irkutsk Incoherent Scatter Radar (IISR) and the Optical Instruments of the National Heliogeophysical Complex of the Russian Academy of Sciences (NHC RAS).
Today, IISR is the only facility in Russia that allows determining the parameters of the entire thickness of the ionosphere using the incoherent scatter method [1], including reconstructing such parameters as the ion and electron temperatures of Ti and Te, as well as the electron concentration of Ne [2].
The aeronomical Fabry-Perot interferometers (FPI) are part of the NHC RAS and are located on the territory of the ISTP SB RAS Geophysical Observatory (Tory, Buryatia) [3]. They are used to observe various characteristics of the natural night airglow, including the 630 nm red line, which allows us to obtain data on changes in atmospheric temperature and wind speed at an altitude of about 260 km. During night observations from August 28 to September 2, the concentration  Ne (according to IINR) and the red glow I630 (according to IFP) showed similar variations. The nature of the dynamics of the Ne profiles suggests that nighttime Ne values ​​are determined by the meridional wind and vertical transport of the neutral component. An estimate of the vertical plasma drift under the action of the wind in the upper atmosphere can be obtained from the condition of plasma stationarity under the action of the Lorentz force, electric field, and collisions with neutral particles. This assessment showed that the nighttime vertical plasma drift (based on the IFP data) correlates well with the vertical dynamics of the ionospheric plasma (according to the IISR); the increase in the I630 intensity occurs simultaneously with the growth of Ne at about 15 UT, when the vertical drift velocity has minimal values. Apparently, the growth of I630 occurs due to the increase in the number of excited oxygen atoms due to the influx of electrons from above.
Our numerical modeling shows that the determining reaction of the excitation of [O] atoms at night is dissociative recombination, the intensity of which is determined by Ne. The change in the number of electrons at an altitude of ~250 km is apparently associated with the dynamics of the neutral wind, including the intensity of the vertical transport. The observed phenomenon indicates the importance of correctly accounting for the neutral wind in the problems of ionosphere modeling and, apparently, indicates the need to introduce the use of the vertical transport of the neutral atmosphere. The demonstrated relationship between Ne and I630, taking into account the dominant role of the only reaction of formation of excited oxygen atoms (dissociative recombination), can serve as a basis for calibrating optical instruments using radiophysical measurements of ionospheric parameters.

   1. Zherebtsov G.A., et al. // Radio Engineering and Electronics. 2002. Vol. 47, N11.P. 1339-1345 [in Russian]
  2. Alsatkin S.S., Medvedev A.V., Ratovsky K.G. // Solar-Terrestrial Physics. 2015. DOI: 10.12737/11450. 
  3. R. V. Vasiliev, et al. // Solar-Terrestrial Physics, 2017, DOI 10.12737/szf-33201707.