Keywords:atmosphere, solar and ionospheric 27-day variations
We believe that the atmospheric influence on relationship between solar and ionospheric variations includes two effects: (1) the delay in the response of thermospheric characteristics relative to the response of the ionization rate to a change in the solar flux, and (2) the presence of a 27-day component in the ionospheric response to atmospheric variations not related to a change in the solar flux. The first effect leads to a delay in the ionospheric 27-day variations relative to the 27-day variations in the solar flux and to different ratios between the amplitudes of the solar and ionospheric components. The second effect reduces the correlation coefficient between the solar and ionospheric components, and also has a significant effect on the delay and amplitude of the ionospheric component. Both effects are studied both theoretically and with measurements. The basis of the theoretical study is the first principles Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) developed in West Department of IZMIRAN. The model gives time-dependent global three-dimensional distributions of (1) the neutral upper atmosphere parameters (temperature, composition, and wind velocity vectors) from 80 to 526 km, (2) the ionosphere parameters (density, temperature, and velocity vectors of atomic and molecular ions and electrons) from 80 km up to 15 Earth radii. For all considered periods the GSM TIP was utilized for model runs with taking into account solar activity variations and without taking into account geomagnetic activity variation. Note that our approach ignores possible changes in the lower atmosphere due to an increase in solar activity. The basis of the observational study is a statistical analysis of 27-day variations in the peak electron density, total electron content, global electron content and solar index F10.7. We assume that atmospheric variations unrelated to changes in solar flux have a strong effect on the peak electron density and a much smaller effect on the global electron content. For this reason, the response in global electron content is expected to better agree with the model calculations compared to the response in the peak electron density. A statistical analysis of both characteristics allows us to verify this assumption.
The reported study was funded by RFBR, Russian-Taiwanese joint research project number 18-55-52006 MHT_a. Experimental data recorded by the equipment of Center for Common Use «Angara» (http://ckp-rf.ru/ckp/3056/) obtained with budgetary funding of Basic Research program II.12 were used.