Long‐term variations in sunspot magnetic field–area relation
|Author:||Nagovitsyn, Y. A.1,2; Pevtsov, A. A.3,4; Osipova, A. A.1|
1Pulkovo Astronomical Observatory, Russian Academy of Sciences, St. Petersburg, Russian Federation
2Saint Petersburg State University of Aerospace Instrumentation, St. Petersburg, Russian Federation
3National Solar Observatory, Sunspot, New Mexico
4ReSoLVE Centre of Excellence, Space Climate Research Unit, University of Oulu, Oulu, Finland
|Online Access:||PDF Full Text (PDF, 4.7 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe201903057225
John Wiley & Sons,
|Publish Date:|| 2019-03-05
Background: Several recent studies indicated possible long‐term variations of physical properties of sunspots.
Materials and Methods: Using observations of sunspot magnetic field strengths (H) from the Crimean Astrophysical Observatory and area (S) of sunspots from the Kislovodsk Mountain Astronomical Station of Pulkovo Observatory, we investigate the changes in the relation between H and S over the period of about two solar cycles (1994– 2013). The data were fitted by H = A + B log S, where A = (778 ± 46) and B = (778 ± 25).
Results: We show that the correlation between H and S varies with the phase of solar cycle, and A coefficient decreases significantly after year 2001, while B coefficient does not change significantly. Furthermore, our data confirm the presence of two distinct populations in the distribution of sunspots (small sunspots with weaker field strength and large sunspots with stronger field). We show that the relative contribution of each component to the distribution of sunspots by their area changes with the phase of solar cycle and on longer‐than‐cycle periods.
Conclusion: We interpret these changes as a signature of a long‐term (centennial) variations in the properties of sunspots.
|Pages:||26 - 34|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
115 Astronomy and space science
Y.A.N. and A.A.O. acknowledge support by the Russian Foundation for Basic Research (RFBR Grant No. 16‐02‐00090) and research program No. 7 of the Presidium of Russian Academy of Sciences, and the Council for support of leading scientific schools of the Russian Federation (grant HIII‐7241.2016.2).
© 2017 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. This is the peer reviewed version of the following article: Nagovitsyn YA, Pevtsov AA, Osipova AA. Long‐term variations in sunspot magnetic field– area relation. Astron. Nachr./AN. 2017;338:26–34, which has been published in final form at https://doi.org/10.1002/asna.201613035.