Chowdhury, P., Kilcik, A. orcid.org/0000-0002-0094-1762, Saha, A. et al. (3 more authors) (2024) Temporal and periodic analysis of penumbra–umbra ratio for the last four solar cycles. Solar Physics, 299 (2). 19. ISSN 0038-0938
Abstract
We investigate the long-term dynamic behavior of the sunspot penumbra to umbra area ratio by analyzing the Debrecen Photoheliographic Data (DPD) of sunspot groups during the period 1976–2017 (Solar Cycles 21–24). We consider all types of spots and find that the average penumbra–umbra ratio does not exhibit any significant variation with spot latitudes, solar-cycle phases as well as sunspot-cycle strengths. However, the behavior of this ratio is different when we consider the latitudinal distribution of the northern and southern hemispheres separately. Our analysis indicates that for daily total sunspot area the average spot ratio varies from 5.5 to 6.5 and for very large sunspots (> 5000 μHem; one μHem is 10−6 the area of visual solar hemisphere) its value rises to about 8.3. In the case of the group sunspot area, the average spot ratio is ∼6.76. Furthermore, we found that this ratio exhibits a trend for both smaller (area <100 μHem) and large (area > 100 μHem) sunspots. Finally, we report the periodic and quasiperiodic variations present in this ratio time series after applying the multitaper method (MTM) and Morlet-wavelet technique. We found that along with the ∼11-year solar-cycle period, the penumbra to umbra area ratio also shows several midterm variations, specifically, Rieger-type and quasibiennial periodicities. We also found that Rieger-type periods occur in all cycles, but the temporal evolution and the modulation of these types of periodicities are different in different solar cycles.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © The Author(s) 2024. Open Access: This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. |
Keywords: | Sunspot: umbra; Sunspot: penumbra; Solar cycle; Wavelet analysis; Periodicity; Sunspots |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > School of Mathematics and Statistics (Sheffield) |
Funding Information: | Funder Grant number SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/M000826/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 21 Feb 2024 12:15 |
Last Modified: | 21 Mar 2024 14:49 |
Status: | Published |
Publisher: | Springer Science and Business Media LLC |
Refereed: | Yes |
Identification Number: | 10.1007/s11207-024-02263-5 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:209365 |