Some Features of the Present-day Transition Period in Solar Activity

Abstract

Various geophysical indices and their prognostic value were analyzed in (Obridko et al., 2013; Kirov et al., 2013, 2015, 2017; Georgieva et al., 2015, 2018). Two indices have been selected for the analysis (total annual Dst values, and duration of a storm). It is important to note that, unlike the other indices of solar and geophysical activity, the summary Dst index does not show violation of the Gnevyshev-Ohl rule. The analysis of annual mean Dst values reveals a clearly pronounced decrease in activity, at least since the 1980-ies. This allows us to suggest that we are at the descending branch of a secular cycle or on the threshold of a Grand Minimum. The decrease in solar activity is corroborated by the analysis of Forbush effects, solar wind speed, and intensity of the near-Earth magnetic field.