Abstract
The results of two-frequency lidar sounding of the atmosphere from the altitudes of 100-500 km are presented. The data were obtained in 2017 at a lidar site located in Kamchatka. One lidar channel is applied to investigate the aerosol formations in the middle atmosphere and to issue the resonance scattering on excited ions of atomic nitrogen in the upper atmosphere. Nd:YAG laser operating on the wavelength of 532 nm is used in this channel. A dye laser with tunable frequency is applied in the second channel. The wavelength of 561.1 nm corresponds to the chosen dipole transition between the excited states of atomic oxygen. Defined light-scattering layers were discovered in the region of 200-400 km. They are caused by presence of excited states of atomic oxygen and nitrogen ions. The possibility of reconstruction of excited ions Nh-profile and determination of precipitated electron fluxes spectra by the lidar method is shown. The possibility of manifesting resonance scattering and formation of imaginary aerosol layers in the middle atmosphere is discussed.
Highlights
Application of resonance scattering effect during laser radiation propagation in the upper atmosphere was first suggested in 1964-1965
It was shown the possibility to determine the energies of precipitated electrons into the atmosphere by the lidar method when sounding at the wavelength of 532 and 561.1 nm
The possibility of detecting resonant scattering by gas components of the middle atmosphere is shown
Summary
Application of resonance scattering effect during laser radiation propagation in the upper atmosphere was first suggested in 1964-1965. For the gas components the resonance scattering cross section has the values from 10−12 cm2sr−1 for helium atom to 10−21 cm2sr−1 for some electron transitions for molecular nitrogen. The authors announce the lidar to investigate excited states of molecular nitrogen ion. The resonance scattering on atomic nitrogen excited ions at the wavelength of 532 nm was discovered in March 2008. Analysis of the geophysical state accompanying the phenomenon allowed us to conclude that a possible physical mechanism explaining these correlations is the resonance scattering on excited nitrogen ions. The resonance scattering on excited ions of atomic oxygen at the wavelength of 561.1 nm was purposefully investigated after lidar station modernization in 2010. The paper presents the results of two-frequency lidar sounding at the wavelengths of these components in autumn 2017
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