Time-dependent properties of sunspot groups I.: Lifetime and asymmetric evolution

Emese Forgács-Dajka, László Dobos, István Ballai (2021.03.01-2021.09.30)
Eötvös University, John Hopkins University, Sheffield University

Abstract: Abstract: Observing the phenomena of solar activity has a long history, so we have the opportunity to study on a long time scale. We aim to study the time dependence of sunspot group areas in a large sample composed of various databases spanning over 130 years, used state-of-the-art statistical methods. For a carefully selected but unbiased sample, we use Bayesian modelling to fit the temporal evolution of the combined umbral and penumbral area of spot groups with a skew-normal function to determine the existence of any asymmetry in spot growth or decay. The great advantage of this method is that we can obtain the properties for the whole lifetime (eg lifetime, different parts of the developmental stages, such as growth and decay part) for which there are no complete data sets from appearance to disappearance. The reason for this is to be found in the observation, i.e. due to the rotation of the Sun. Our results robustly support our hypothesis that there are two types of groups: (i) one that develops rapidly after appearance but decomposes more slowly, and (ii) one that grows more slowly and decays faster. In addition, we used the model parameters to examine the lifetime of the sunspot groups and the relationships between lifetime and maximum area.

Publication: Astronomy & Astrophysics, Volume 653, id.A50, 10 pp. DOI: 10.1051/0004-6361/202140731 arXiv: arXiv:2106.04917 Publisher link: https://www.aanda.org/articles/aa/pdf/2021/09/aa40731-21.pdf

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