Abstract
We present an analysis of observations of the indices of the sunspot numbers (SSN from the National Oceanic and Atmospheric Administration (NOAA)), the radio-emission flux at a wavelength of 10.7 cm (F 10.7), and the Total Solar Irradiance (TSI) in cycles 22–24. We have found that the ratio of the observed values SSNobs to the calculated ones SSNsyn (from the regression relations between SSN and F 10.7) decreases after 1990 by 20–25%, rather than by 35%, as was supposed earlier. The characteristics of the most widely used SSN index, such as the decrease in sunspot numbers and magnetic field strength in small and medium spots, do not change in complete correspondence to the expected scenario of the solar activity development predicted from the flux F 10.7 in cycles 23 and 24; they also cannot be fully explained by an additional minimum of the secular cycle. We also showed that the observed SSN changes lead to an increase of the Total Solar Irradiance in activity cycles 23–24 as compared to that in cycle 22.
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Bruevich, E.A., Yakunina, G.V. General trends in the change in solar activity indices in the period from the late XX to early XXI century. Geomagn. Aeron. 55, 1060–1065 (2015). https://doi.org/10.1134/S0016793215080058
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DOI: https://doi.org/10.1134/S0016793215080058