HF radio wave propagation in conditions of prolonged low solar activity

An unusually long period of very low solar activity was of great interest. Investigation of the characteristics of radio propagation in the European region during this period shows that correspondence between the experimental and IRI model parameters foF2, hmF2, TEC, M3000, MUF3000 may be worse than during moderate activity periods. The disturbed state in this period is characterized by the index Dst, not falling below -100nT, 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 total electron content TEC. To determine the N(h)-profile of the topside ionosphere the model IRI-Plas can be used, allowing adaptation to the experimental values of foF2 and TEC.