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Differential Rotation of Recurrent Sunspots in Solar Cycles 23–25 KCI 등재 SCOPUS

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  • URLhttps://db.koreascholar.com/Article/Detail/449069
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천문학회지 (Journal of The Korean Astronomical Society)
한국천문학회 (Korean Astronomical Society)
초록

In this study, we explore the solar differential rotation using recurrent sunspots observed by space-borne instruments from August 1996 to June 2025. To avoid systematic errors, the differential rotation profiles are calculated taking into account both Earth’s elliptical orbit and the inclination of the solar rotation axis to the ecliptic. We have found that the equatorial rotation rate first increases and then decreases in Solar Cycles 23, 24, and 25, which can be interpreted as torsional oscillations with a period of approximately 11 years. When comparing the angular rotation rates at the solar maximum and minimum, the latitudinal gradient of rotations at solar minima exhibits significant cycle-to-cycle variation. During the descending phase, the latitudinal gradient of rotations changes significantly between solar cycles. The latitudinal gradient of rotations in the northern hemisphere is comparable across solar cycles, whereas that in the southern hemisphere displays significant modulations across solar cycles. In terms of the Zürich sunspot classification system, the equatorial rotation rate is higher and the differential rotation is stronger for J-type groups than for H-type groups. It is also attempted to investigate the dependence on the order of successive passages, revealing that although the equatorial rotation rates for the first and second passages are similar, the differential rotation for the second passage appears significant. This is indicative of less rigid rotation during the second passage. To conclude, we point out that the Sun appears to rotate more differentially in the case that the solar magnetic activity is relatively weaker, when comparing cases of weak and strong solar activity.

목차
Introduction
Data and Methods
    Data
    Identification of Recurrent Sunspots
    Conversion of Synodic Period to Sidereal Period
    Rotation Rate as a Function of Helio-latitude
Differential Rotation Rates
    Solar Cycles
    Solar Phases
    Solar Hemispheres
    Sunspot Types
    Number of Passages
    Activity Level
Summary and Conclusions
Acknowledgments
References
저자
  • Hyo-Geun Ji(Department of Earth Science Education, Seoul National University, Seoul 08826, Korea)
  • Sung-Jin Oh(Butterstar Observatory, Dongduchen High School, Dongduchen-si 11314, Korea)
  • Jeong-In Yeo(Department of Science Education, Ewha Womans University, Seoul 03760, Korea)
  • Heon-Young Chang(Department of Astronomy, Kyungpook National University, Daegu 41566, Korea) Corresponding author