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Effects of a series of large flares from a sunspot group eruption on VLF propagation
Sunspot groups are constantly evolving, causing flare eruption under the action of the solar atmospheric magnetic field. After the flare, the ejected...
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Group Sunspot Numbers: A New Reconstruction of Sunspot Activity Variations from Historical Sunspot Records Using Algorithms from Machine Learning
Historical sunspot records and the construction of a comprehensive database are among the most sought after research activities in solar physics....
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Cyclical Behaviors of Sunspot-Group Tilt Angles in Solar Cycles 21 – 23
Based on the Debrecen Photoheliographic Data (DPD) sunspot catalog, we investigate the cyclical behaviors of tilt angles of all sunspot groups (SGs)...
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Sunspot Observations at the Eimmart Observatory: Revision and Supplement
Digital images of sunspot drawings of the archives of Georg Christoph Eimmart stored at the National Library of Russia, St. Petersburg, are analyzed...
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Sunspot extraction and hemispheric statistics of YNAO sunspot drawings using deep learning
Sunspot drawings around the globe provide long historical records for understanding the long-term trends in the solar activity cycle. Yunnan...
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On the Periodicities in Solar Rotation and Activity Determined from Sunspot-Group Data and Possible Connection with Rossby-Like Waves
Analyses of solar rotation and activity, and their variations, can improve the understanding of the formation and interaction of the solar-activity...
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Two Populations of Sunspot Groups and Their Meridional Motions
It is shown that the average meridional velocities of sunspot groups linearly depend on their average longitudinal velocities (solar rotation) with a...
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High-Resolution Observation of Blowout Jets Regulated by Sunspot Rotation
Coronal jets are believed to be the miniature version of large-scale solar eruptions. In particular, the eruption of a minifilament inside the base...
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Data-Driven Forecasting of Sunspot Cycles: Pros and Cons of a Hybrid Approach
Understanding the number of sunspots is crucial for comprehending the Sun’s magnetic-activity cycle and its influence on space weather and the Earth....
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Reconstructing Sunspot Number by Forward-Modelling Open Solar Flux
The open solar flux (OSF) is the integrated unsigned magnetic flux leaving the top of the solar atmosphere to form the heliospheric magnetic field....
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Hemispheric Sunspot Numbers from the Astronomical Observatory of the University of Valencia (1940 – 1956)
In this work, we present hemispheric sunspot number counts made in the Astronomical Observatory of the University of Valencia for the period...
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Rudolf Wolf to Alfred Wolfer: The Transfer of the Reference Observer in the International Sunspot Number Series (1876–1893)
In 1876, Alfred Wolfer started observing the Sun and recording the properties of sunspots alongside Rudolf Wolf. Their observations became the basis...
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Automated Sunspot Detection as an Alternative to Visual Observations
We developed an automated method for sunspot detection using digital white-light solar images to achieve a performance similar to that of visual...
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Iterative Construction of the Optimal Sunspot-Number Series
The relative number of sunspots represents the longest evidence describing the level of solar activity. As such, its use goes beyond solar physics,...
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Chinese sunspot drawings and their digitization – (V) the phase relation between Hα flare index and sunspot activity
H α flare index is one of the solar activity indicators to describe the physical properties of the active regions in the solar atmosphere. Sunspot...
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Association of solar flares with magnetic complexity of the sunspot groups in solar active regions during solar cycles 23–25
The present study aims to investigate the association of X-ray solar flares with the magnetic complexity of sunspot groups in active regions for the...
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Hemispheric Asymmetry in the Sunspot Cycle as a Nonextensive Phenomenon
The appearance of dark sunspots over the solar photosphere is not considered to be symmetric between the northern and southern hemispheres. Among the...
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Rediscovery of 23 Historical Records of Naked-Eye Sunspot Observations in AD 1618
The year 1618 was once regarded as a minimum of the first observed solar cycle or even the beginning of the extended Maunder minimum. However, new...
