Influence of meteorological and wave processes on the lower ionosphere during solar minimum conditions according to the data on midlatitude VLF-LF propagation

Modeling of the lower ionosphere climate

“…As was mentioned in the Introduction, this work considers the five component model based on the nitric oxide ionization process as a local model of the ionospheric D region [22,26]. The usage of this model is related to several factors.…”

“…It was also independently indicated that the effect of the meteorological factors (temperature, moisture concentration, carbon dioxide, etc.) is considerable [24][25][26]. The climatological phenomenon of increased day to day variations in the radiowave absorption in the winter D region (the ionospheric radio absorption winter anomaly) is of special signifi cance [27].…”

“…Sensitive incoherent scatter radars that appeared in the last decade [32,33], as well as riome ters [34] and ULF-LF stations [26], make it possible to obtain continuous series of rather accurate mea surements of the D region local state. We emphasize that a substantial singularity of the ionospheric D region consists in that it is relatively simple to describe the region global state under the condi tions of strong disturbances (such as solar flares or particle ingressions in the polar cap) and com plex physicochemical processes under quiet condi tions [35].…”

“…This model describes 36 positive and 29 negative ions, 13 neutral constituents, and about 400 chemical reac tions. In our country semiempirical models of the ion ospheric D region for solving applied problems of radiowave propagation are developed, e.g., at the Institute of Geosphere Dynamics (IDG RAS) [26,37]. Note that factually the only coupled model of the neutral atmosphere and ionosphere (NCAR TIME GCM), resolving the D region [38], uses a six compo nent photochemical model as a component numerical block [21].…”

“…In this work we consider the five component local photochemical model, which was proposed by the IDG RAS team and is successfully used to solve applied problems of the ULF-LF radiowave propaga tion in a quiet ionosphere [22,26], as the first version of the ionospheric D region model. This simple iono spheric model in the initial statement for the coupled modeling of the neutral and charged constituents is used to estimate the effect of the middle atmosphere thermal dynamics on the D region characteristics that can be called the D region climate (including the mean state and the medium variability).…”