Published online by Cambridge University Press: 27 November 2018
Reconstruction of regions with an open configuration of magnetic force lines was carried out according to synoptic Hα maps over a period of more than 100 years. It is shown that the maximum area of open structures in the cycle of solar activity is reached in the descending phase, 1÷2 years before the onset of the minimum. The total area of open structures in the current cycle n has a high correlation (r ~ 0.8) with the amplitude of the next activity cycle n + 1. There is also a secular envelope with a maximum in the middle of the 20th century.