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Astronomy & Astrophysics
Alexander Mordvinov, Bidya Binay Karak, Dipankar Banerjee, Elena M. Golubeva, Anna Khlystova, Anastasiya Zhukova, Pawan Kumar
Summary: Detailed study of solar activity cycles reveals important conclusions about polar field reversals and the causal relationship between polar field formation and magnetic flux transport. The characteristics of different solar activity cycles are influenced by the spatiotemporal organization and properties of emergent magnetic flux, leading to complex restructuring of high-latitude magnetic fields.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. Javaraiah
Summary: The study analyzed sunspot-group data and found a significant latitude-time dependence in both the residual rotation rate and meridional motion. There is a strong correlation between the slope and sunspot number, indicating a relationship between activity and angular momentum transport towards the equator. However, the cycle-to-cycle modulations in the slope show insignificant correlation with the strength of activity on a long-time scale.
Article
Astronomy & Astrophysics
Qirong Jiao, Jie Jiang, Zi-Fan Wang
Summary: This study investigates the tilt angles of sunspot groups in relation to the generation of the poloidal magnetic field in the Babcock-Leighton dynamo. The results show that the tilt coefficient is indeed anti-correlated with the cycle strength, with strong statistical significance. Different methods in handling uncertainties were found to be responsible for the controversial nature of previous results. Additionally, the study reveals a linear vs. square-root dependence of tilts on latitudes for weak vs. strong cycles.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Soumyaranjan Dash, Dibyendu Nandy, Ilya Usoskin
Summary: This study utilizes simulations and observational data to reveal the impact of magnetic fields generated by the Sun's internal dynamo mechanism on the variations of the solar corona and the state of the heliosphere, establishing causality between solar internal variations and the state of the heliosphere.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
V. V. Zharkova, I Vasilieva, E. Popova, S. J. Shepherd
Summary: We study the relationship between the averaged sunspot numbers (SSN) and a modulus summary curve (MSC) obtained from principal component analysis of the solar background magnetic field (SBMF). The MSC is closely correlated with the whole set of SSN, except for discrepancies in a few cycles in the 18th and 19th centuries. Wavelet and Fourier analysis reveal a prominent 10.7-year cycle in both SSN and MSC series, but the SSN series also show a 101-year cycle while the MSC series show a 342-year cycle close to the red-noise level. The correlation coefficients between SSN and MSC vary depending on the data sets, indicating their close but not identical relationship representing different entities of solar activity.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Irina N. Kitiashvili
Summary: The study demonstrates that reliable solar activity predictions can be made using relatively short time-series of sunspot numbers, with the accuracy of the predictions having weak dependence on the length of available observations. At least three cycles of observations are needed to obtain robust forecasts.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Rohan E. Louis, Avijeet Prasad, Christian Beck, Debi P. Choudhary, Mehmet S. Yalim
Summary: By studying the solar chromosphere in a sunspot light bridge, it was found that strong electric currents can lead to temperature excess and thermal enhancements in the chromosphere. The thermal effects are primarily concentrated in the height range of 0.4-0.7 Mm above the light bridge.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
X. J. Zhang, L. H. Deng, Y. Fei, C. Li, X. A. Tian, Z. J. Wan
Summary: Hemispheric asymmetry of solar magnetic structures is an important feature of solar cycles. A long-term study using data from the National Astronomical Observatory of Japan reveals a correlation between the sunspot relative numbers and international sunspot numbers, suggesting periodic variations in hemispheric asymmetry. The findings provide insights into the mechanism responsible for the generation and variation of hemispheric coupling in the Sun.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
J. Javaraiah
Summary: There is a small but statistically significant north-south asymmetry in solar activity indices, with implications on the solar dynamo mechanism. The results suggest that the amplitude of Solar Cycle 25 would be 25-40% smaller than that of Solar Cycle 24.
ASTROPHYSICS AND SPACE SCIENCE
(2021)
Article
Astronomy & Astrophysics
Hechao Chen, Hui Tian, Leping Li, Hardi Peter, Lakshmi Pradeep Chitta, Zhenyong Hou
Summary: The study found that sunspot supersonic downflows (SSDs) primarily appear at the footpoints of sunspot plumes and are temporally associated with the appearance of chromospheric bright dots inside the sunspot. Dual-perspective extreme-ultraviolet imaging observations revealed a large-scale closed magnetic loop system spanning the sunspot region and a remote region. The research also demonstrated that these SSDs are caused by the formation of large-scale coronal rain due to magnetic field reconnection, which flows along these closed magnetic loops towards the sunspot.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
Yogesh, D. Chakrabarty, N. Srivastava
Summary: The study reveals significant differences in the relative abundance of alpha particles in solar cycle 24 compared to the previous three cycles, potentially influenced by changes in corona magnetic field configuration.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Lijuan Liu, Jiajia Liu, Jun Chen, Yuming Wang, Guoqiang Wang, Zhenjun Zhou, Jun Cui
Summary: By studying the data provided by the Helioseismic and Magnetic Imager and the Atmospheric Imaging Assembly on-board the Solar Dynamics Observatory, it was found that the collision between two newly emerged spot groups forms a delta sunspot. A complex flux rope structure was identified above the collision location, with a multilayer configuration and a null point located above it.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Astronomy & Astrophysics
Ratul Das, Aparup Ghosh, Bidya Binay Karak
Summary: This study investigates the hemispheric asymmetry of the sunspot cycle through nonlinear time series analysis, finding that the asymmetry is largely governed by stochastic noise but also exhibits long-term persistence originating from irregular processes in the solar dynamo. The long-term persistence in the solar cycle asymmetry suggests that the solar magnetic field has some memory in the convection zone.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Y. Liu, G. P. Ruan, B. Schmieder, S. Masson, Y. Chen, J. T. Su, B. Wang, X. Y. Bai, Y. Su, W. Cao
Summary: In this study, a small fan-shaped jet observed on a light bridge on the Sun was investigated. The analysis suggests that the jet may have resulted from magnetic reconnection in the highly diverging magnetic field below the chromosphere. However, the expected opposite magnetic polarity at the base of the jet was not found, leading to the consideration of alternative physical mechanisms.
ASTRONOMY & ASTROPHYSICS
(2022)
Article
Astronomy & Astrophysics
V. M. S. Carrasco, H. Hayakawa, C. Kuroyanagi, M. C. Gallego, J. M. Vaquero
Summary: The study compared the solar activity levels of the Maunder Minimum in 1709 with the Dalton Minimum and recent solar cycles, finding that 1709, while one of the most active years, was less active compared to other years in those periods. This provides robust evidence of low solar activity levels in the Maunder Minimum.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Eva Robbrecht, Spiros Patsourakos, Angelos Vourlidas
ASTROPHYSICAL JOURNAL
(2009)
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Astronomy & Astrophysics
Y. -M. Wang, E. Robbrecht
ASTROPHYSICAL JOURNAL
(2011)
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Astronomy & Astrophysics
Y. -M. Wang, R. Grappin, E. Robbrecht, N. R. Sheeley
ASTROPHYSICAL JOURNAL
(2012)
Article
Astronomy & Astrophysics
Eva Robbrecht, Yi-Ming Wang
ASTROPHYSICAL JOURNAL LETTERS
(2010)
Article
Astronomy & Astrophysics
B. J. Lynch, Y. Li, A. F. R. Thernisien, E. Robbrecht, G. H. Fisher, J. G. Luhmann, A. Vourlidas
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2010)
Article
Astronomy & Astrophysics
Andy Devos, Cis Verbeeck, Eva Robbrecht
JOURNAL OF SPACE WEATHER AND SPACE CLIMATE
(2014)
Article
Astronomy & Astrophysics
E Robbrecht, D Berghmans
ASTRONOMY & ASTROPHYSICS
(2004)
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Astronomy & Astrophysics
E Robbrecht, E Verwichte, D Berghmans, JF Hochedez, S Poedts, VM Nakariakov
ASTRONOMY & ASTROPHYSICS
(2001)
Article
Astronomy & Astrophysics
JF Hochedez, A Zhukov, E Robbrecht, R Van der Linden, D Berghmans, P Vanlommel, A Theissen, F Clette
ANNALES GEOPHYSICAE
(2005)