Forty years of measurements of the mean magnetic field of the Sun. An insight from today

  • V.A. Kotov Crimean Astrophysical Observatory, Nauchny, 298409

Abstract

Over the last 40 years the CrAO and five other observatories of the world have carried out more than 18.5 thousand (daily) measurements of the mean magnetic field, MMF, of the Sun-as-a-star. The main MMF periodicity is caused by the Sun’s equatorial rotation with a synodic period of 26.92 ± 0.02 d (it was stable over decades but become “bifurcated” in the 23d cycle). It is shown that (a) the average sidereal period of the equator, 25.122 ± 0.010 d, occures to be in close resonant relations with the orbital and axial rotations of Mercury (5:2 and 5:3, respectively), (b) the most powerful longer period, 1.036 ± 0.007 yr, is suspiciously close to the Earth’s orbital period and (c) coincides with the average synodic period of revolution of giant planets 1.036 ± 0.020 yr, (d) the MMF reveals a substantial period of 1.58 ± 0.02 yr which agrees, within the error limits, with the synodic period 1.60 yr of Venus, and also (e) a significant periodicity 19.8 ± 2.5 yr connected plausibly with the 22-year magnetic cycle of the Sun. The origin of all these periodicities seems to be mysterious.

It is supposed that the resonances have emerged at the early stages of the formation of the Solar system, and their existence at the present epoch is caused by the peculiar structure and dynamics of the central core of our star. It is found that the average, over 40 years, MMF level is practically zero: -0.018  ±  0.015 G. We draw also attention to an abnormal behaviour of the cycle 23, manifested in: (1) the violation of the Gnevyshev-Ol’s rule for the pair of cycles 22-23, (2) the accelerated, by 1.2 %, rotation of the solar equator, and (3) a substantial increase of the length of the cycle (not less than 11.5 yr) as compared with the average length of the cycle in 20th century (10.5 yr). A problem of the so-called solar magnetic “monopole” is briefly discussed.

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Published
2009-06-01
How to Cite
Kotov V., 2009. Izvestiya Krymskoi Astrofizicheskoi Observatorii, vol. 105, no. 1, pp. 75-90. Available at: https://jn.craocrimea.ru/index.php/izvcrao/article/view/883 (Accessed: 5December2020)
Section
Research articles