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• Large-scale traveling ionospheric disturbances (LSTID) were observed over Europe. • Two types of LSTIDs were found during the moderate storm from the ionosonde data. • Incoherent scatter data enabled the detection of additional LSTIDs over Ukraine. • Phase and onset differences of oscillations in F2 peak parameters were established. We present the results of ground based remote sensing observations of large-scale traveling ionospheric disturbances (LSTIDs) occurring during the moderate magnetic storm evolution (22–24 September 2020) over central and eastern Europe. Three ionosondes located in Juliusruh, Pr u ˚ honice and near Kharkiv, and the Kharkiv incoherent scatter radar were employed to study temporal and spatial LSTID signatures in ionospheric F2 peak density and height and electron density variations at the heights of 100–300 km. Two types of LSTIDs are detected, which are originated during enhancement in auroral activity (2 events) and local sunrise terminator passage (3 events) from the ionosonde data. The magnetic storm-related LSTIDs exhibit equatorward propagation with the horizontal phase velocities of 546 m/s and 576 m/s, similar dominant periods of 135–150 min and 165–180 min over all three sites and a longitudinal dependence in fractional (relative) amplitudes of electron density perturbation. The solar terminator induced LSTIDs demonstrate the variety in both relative amplitudes and dominant periods over different locations. They have a westward apparent horizontal phase velocities of 288–345 m/s, which are close to the solar terminator velocity at ionospheric heights. Employment of incoherent scatter data enabled the detection of additional LSTIDs over Ukraine with the periods in a broader range of 41–168 min, an establishment of phase and onset differences for the oscillations in the ionospheric F2 peak electron density and height. [ABSTRACT FROM AUTHOR]

In the present study, the results obtained by incoherent scatter radar (ISR) and empirical models (NeQuick2 and IRI-2016) of the variations in mid-latitude ionospheric electron density during partial solar eclipses on March 29, 2006 and March 20, 2015 over Kharkiv (49.60° N, 36.30° E, Ukraine) are presented and the prediction performances of the models during these partial solar eclipses are compared. The electron density (Ne) values are obtained for seven (190, 210, 240, 290, 340, 410, and 490 km) different altitudes. The percent deviation of Ne values, statistical correlation coefficient and root mean square error (RMSE) during solar eclipses are applied to make this investigation. According to the percent deviation of Ne values measured by ISR, a decrease in electron density was observed at all heights during the eclipse of March 29, 2006, whereas there was a decrease in Ne values at only 190, 210, and 240 km altitudes during the eclipse of March 20, 2015. However, at other altitudes (290, 340, 410, and 490 km), the increase has occurred in the electron density during the eclipse on March 20, 2015. The IRI-2016 model predicted that Ne values increase at all altitudes in the solar eclipse on March 20, 2015, and a decrease in Ne at all altitudes occurs on March 29, 2006. It can be said that the NeQuick 2 model predicts a decrease in the first three heights and an increase in other heights. When the predictions of the empirical models were compared, according to the root mean square error (RMSE) calculations, the predictions of the IRI-2016 model can be said to be better than that of NeQuick 2 at all heights during eclipse of March 29, 2006. Besides, the IRI-2016 model's prediction can be stated to be better than NeQuick 2 model at the first three altitudes (190, 210 and 240 km), while the NeQuick 2 model's prediction can be said to be better than the IRI-2016 model at the last four (290, 340, 410, and 490 km) altitudes during March 20, 2015 eclipse. It can be stated that ionospheric models do not accurately reflect the ionospheric response to partial solar eclipses. The inclusion of ISR data in empirical models will help models accurately predict the ionospheric response under all conditions. [ABSTRACT FROM AUTHOR]

Research on solar eclipses has been a very importance in detecting short and medium-scale changes in the ionosphere. In this paper, the relationship between the changes in self-diffusion coefficients of the O+ + N² → NO+ + N reaction with the solar eclipse of March 29th, 2006 in Kharkov, Ukraine (49.6° N and 36.3° E) was investigated for 202, 252, and 303 km. The results of the research showed that self-diffusion coefficients increases with the increase of ionospheric altitude in each three days and the maximum diffusion value is reached at 303 km on 29th of March. It can be said that results of effects of solar eclipse in Turkey on ionosphere, results of the study of the experimental measurement and obtaining results of our study are consistent with one another. [ABSTRACT FROM AUTHOR]