O.A. Maltseva, N.S. Moshaeva, T.N. Nikitenko
A long period of extremely low solar activity occurred first in the history of modern geophysical and radio physical observations, therefore, aroused great interest and the number of publications. In general, these publications are devoted to features of physical processes on the Sun and their impact on the environment. This paper discusses specific aspects of interest to the propagation of radio waves. Correspondence between the experimental and IRI model parameters foF2, hmF2, TEC, M3000, MUF3000 may be worse than during moderate and high activity periods. Geophysical situation is characterized by weak and moderate disturbances (Dst>–80nT) and positive bursts of TEC. During such disturbances and bursts, changes in TEC and foF2, MUF occur synchronously. This allows to use the experimental median equivalent thickness of the ionosphere for the determination of foF2, MUF from the TEC. Bursts of TEC lead to essential changes of N(h)-profile of the topside ionosphere. These changes can be taken into consideration by the IRI-Plas model.