Main Article Content

Serge Koutchmy
Boris Filippov
E. Tavabi
J-C. Noëns
O. Wurmser


The forthcoming solar cycle (SC) 25 was believed to be rather low when the sunspot number (SN) is used as a measure of the activity level. The most popular prediction was made by the NOAA/NASA Solar Cycle 25 Prediction Panel in 2019, including works based on dynamo-type models. However, we discovered that the height of SC25 could be high, using different observations for measurements of the level of the polar-region activity above the limb at high latitudes several years before the start of SC25 and also after its beginning in 2020. The polar-region activity, which we consider, seems to be related to the polar coronal-hole (CH) activity, and it was significantly higher before SC25 than before SC24. It is also possibly reflected in the so-called chromospheric prolateness observed at solar minimum. Accordingly, we suggest that SC25 could indeed be significantly higher than SC24, which was a very low SN cycle.


Download data is not yet available.

Article Details

How to Cite
Koutchmy S., Filippov B., Tavabi E., et al., 2022. Acta Astrophysica Taurica, vols. 3, nos. 2, pp. 12–16. DOI: 10.34898/aat.vol3.iss2.pp12-16
Magnetism and activity of the Sun and stars – 2021 Conference proceedings


Filippov B., Koutchmy S., 2000. Solar Phys., vol. 196, no. 2, pp. 311–320.

Filippov B., Koutchmy S., Vilinga J., 2007. Astron. Astrophys., vol. 464, no. 3, pp. 1119–1125.

Kitiashvili I.N., 2020. In Kosovichev A.G., Strassmeier K., and Jardine M. (Eds), Solar and Stellar Magnetic Fields: Origins and Manifestations, Proceedings IAU Symposium, vol. 354, pp. 147–156.

Kitiashvili I.N., 2021. Mon. Not. Roy. Astron. Soc., vol. 505, iss. 4, pp. 6085–6102.

Koutchmy S., di Folco E., Auchere Fr., et al., 1999. In Vial J.-C. and Kaldeich-Schu B. (Eds), 8th SOHO Workshop: Plasma Dynamics and Diagnostics in the Solar Transition Region and Corona, ESA Special Publication, vol. 446, p. 385.

Makarov V.I., Leroy J.L., Noens J.C., 1987. Sov. Astron., vol. 31, p. 560.

Murray N., 1992. Solar Phys., vol. 38, pp. 419–422.

Nandy D., 2021. Solar Phys., vol. 296, no. 3, eid. 54.

Noens J.-C., Wurmser O., 2000. Astrophys. Space Sci., vol. 273, pp. 17–23.

Svalgaard L., Duvall T.L., Scherrer P.H., 1978. Solar Phys., vol. 58, pp. 225–239.

Tlatov A.G. 2009. Solar Phys., vol. 260, pp. 465–477.

Tlatov A.G. and Tlatova K.A., 2020. Geomagnetism and Aeronomy, vol. 60, no. 7, pp. 825–830.