Agora – Project report

Prediction of the amplitude of solar cycle 25 using polar faculae observations

Solar-Terrestrial Centre of Excellence (STCE), Royal Observatory of Belgium, Avenue Circulaire 3, Brussels 1180, Belgium

^* Corresponding author: jan.janssens@oma.be

Received: 7 May 2020
Accepted: 24 December 2020

Abstract

Based on the monthly number of polar faculae, a forecast of the amplitude of solar cycle 25 (SC25) is provided, as well as a prediction of the number of solar flares. Faculae near both solar poles have been visually observed using a commercial off-the-shelf 20 cm Schmidt-Cassegrain telescope since 1995. The monthly averages were corrected for varying seeing conditions and the heliographic latitude of the center of the solar disk B₀. From the deduced relationship between the smoothed number of monthly polar faculae during the solar cycle minimum, and the subsequent maximum of the monthly sunspot number, a prediction has been made for the amplitude of the next solar cycle. The methodology used can be considered as a precursor technique. The expected number of M- and X-class flares was calculated based on a statistical approach. The maximum of SC25 is predicted to be 118 ± 29, of similar strength than the previous SC24. Also the number of M5 or stronger flares is expected to be comparable to that of the previous solar cycle.