Abstract
The partial reflection facility of the Polar Geophysical Institute (the
Tumanny observatory, 69.0N, 35.7E) has observed behavior of the
high-latitude lower ionosphere during the 20 March 2015 total solar
eclipse. There were several effects during the eclipse. At the heights
of 60–80 km the ionosphere has shown the effect of a “short night”,
but at the higher altitudes local enhanced electron concentration had a
wave-like form. Data received by the riometer of the Tumanny observatory
have also shown wave-like behavior. The behavior can be explained by
influence of acoustic-gravity waves which originated after cooling of
the atmosphere during the lunar shadow supersonic movement, and
transport processes during the eclipse. During the 21 August 2017 solar
eclipse there was a substorm at the high latitudes. But after the end of
the substorm in the region of the Tumanny observatory the observed
amplitudes of the reflected waves had wave effects which could be
connected with the coming waves from the region of the eclipse. The wave
features were also shown in the behavior of the total electron content
(TEC) of the lower ionosphere. During several solar eclipses it was
implemented observations of lower ionosphere behavior by the partial
reflection facility of the Tumanny observatory. The consideration of the
lower ionosphere TEC had revealed common features in the TEC behavior
during the eclipses. The photochemical theory of processes in the lower
ionosphere is very complicated and up to now it is not completely
developed. Therefore introduction of the effective coefficients
determining the total speed of several important reactions has been
widely adopted when modeling the D-region of the ionosphere. However,
experimental opportunities for obtaining effective recombination
coefficients are rather limited. One of the methods to estimate
effective recombination coefficients uses the phenomenon of a solar
eclipse. During solar eclipses at the partial reflection facility of the
Tumanny observatory observations were carried out. It gave possibility
to obtain the behavior of the electron concentration in time at the
selected heights. Using the obtained experimental profiles, the
effective recombination coefficients at the D-region heights of the
ionosphere have been evaluated.