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Sunspot tilt angles revisited: Dependence on the solar cycle strength
Jiao, Qirong1,2; Jiang, Jie1,2; Wang, Zi-Fan3,4
2021-09-03
Source PublicationASTRONOMY & ASTROPHYSICS
ISSN0004-6361
Volume653Pages:14
AbstractContext. The tilt angle of sunspot groups is crucial in the Babcock-Leighton (BL) type dynamo for the generation of the poloidal magnetic field. Some studies have shown that the tilt coefficient, which excludes the latitudinal dependence of the tilt angles, is anti-correlated with the cycle strength. If the anti-correlation exists, it will be shown to act as an effective nonlinearity of the BL-type dynamo to modulate the solar cycle. However, some studies have shown that the anti-correlation has no statistical significance. Aims. We aim to investigate the causes behind the controversial results of tilt angle studies and to establish whether the tilt coefficient is indeed anti-correlated with the cycle strength. Methods. We first analyzed the tilt angles from Debrecen Photoheliographic Database (DPD). Based on the methods applied in previous studies, we took two criteria (with or without angular separation constraint Delta s > 2 degrees.5) to select the data, along with the linear and square-root functions to describe Joy's law, and three methods (normalization, binned fitting, and unbinned fitting) to derive the tilt coefficients for cycles 21-24. This allowed us to evaluate different methods based on comparisons of the differences among the tilt coefficients and the tilt coefficient uncertainties. Then we utilized Monte Carlo experiments to verify the results. Finally, we extended these methods to analyze the separate hemispheric DPD data and the tilt angle data from Kodaikanal and Mount Wilson. Results. The tilt angles exhibit an extremely wide scatter due to both the intrinsic mechanism for its generation and measurement errors, for instance, the unipolar regions included in data sets. Different methods to deal with the uncertainties are mainly responsible for the controversial character of the previous results. The linear fit to the tilt-latitude relation of sunspot groups with Delta s > 2 degrees.5 of a cycle carried out without binning the data can minimize the effect of the tilt scatter on the uncertainty of the tilt coefficient. Based on this method the tilt angle coefficient is anti-correlated with the cycle strength with strong statistical significance (r = -0.85 at 99% confidence level). Furthermore, we find that tilts tend to be more saturated at high latitudes for stronger cycles. The tilts tend to show a linear dependence on the latitudes for weak cycles and a square-root dependence for strong cycles. Conclusions. This study disentangles the cycle dependence of sunspot group tilt angles from the previous results that were shown to be controversial, spurring confusion in the field.
KeywordSun: magnetic fields sunspots Sun: activity dynamo
Funding OrganizationNational Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS
DOI10.1051/0004-6361/202141215
WOS KeywordBIPOLAR MAGNETIC REGIONS ; FLUX TRANSPORT ; ACTIVE REGIONS ; JOYS LAW ; FIELD ; DEBRECEN ; POLARITY
Language英语
Funding ProjectNational Natural Science Foundation of China[11873023] ; National Natural Science Foundation of China[11522325] ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS[ZDBS-LY-SLH013] ; B-type Strategic Priority Program of CAS[XDB41000000]
Funding OrganizationNational Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; Fundamental Research Funds for the Central Universities of China ; Fundamental Research Funds for the Central Universities of China ; Key Research Program of Frontier Sciences of CAS ; Key Research Program of Frontier Sciences of CAS ; B-type Strategic Priority Program of CAS ; B-type Strategic Priority Program of CAS
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000692222300008
PublisherEDP SCIENCES S A
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Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/75404
Collection中国科学院国家天文台
Corresponding AuthorJiang, Jie
Affiliation1.Beihang Univ, Sch Space & Environm, Beijing, Peoples R China
2.Key Lab Space Environm Monitoring & Informat Proc, Beijing, Peoples R China
3.Chinese Acad Sci, Natl Astron Observ, Key Lab Solar Act, Beijing 100101, Peoples R China
4.Univ Chinese Acad Sci, Sch Astron & Space Sci, Beijing, Peoples R China
Recommended Citation
GB/T 7714
Jiao, Qirong,Jiang, Jie,Wang, Zi-Fan. Sunspot tilt angles revisited: Dependence on the solar cycle strength[J]. ASTRONOMY & ASTROPHYSICS,2021,653:14.
APA Jiao, Qirong,Jiang, Jie,&Wang, Zi-Fan.(2021).Sunspot tilt angles revisited: Dependence on the solar cycle strength.ASTRONOMY & ASTROPHYSICS,653,14.
MLA Jiao, Qirong,et al."Sunspot tilt angles revisited: Dependence on the solar cycle strength".ASTRONOMY & ASTROPHYSICS 653(2021):14.
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