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Impact of Anomalous Active Regions on the Large-scale Magnetic Field of the Sun

Pal, Shaonwita; Bhowmik, Prantika; Mahajan, Sushant S.; Nandy, Dibyendu

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Shaonwita Pal

Sushant S. Mahajan

Dibyendu Nandy


One of the major sources of perturbation in the solar cycle amplitude is believed to be the emergence of anomalous active regions that do not obey Hale's polarity law and Joy's law of tilt angles. Anomalous regions containing high magnetic flux that disproportionately impact the polar field are sometimes referred to as "rogue regions." In this study, utilizing a surface flux transport model, we analyze the large-scale dipole moment buildup due to the emergence of anomalous active regions on the solar surface. Although these active regions comprise a small fraction of the total sunspot number, they can substantially influence the magnetic dipole moment buildup and subsequent solar cycle amplitude. Our numerical simulations demonstrate that the impact of "anti-Joy" regions on the solar cycle is similar to those of "anti-Hale" regions. We also find that the emergence time, emergence latitude, relative number, and flux distribution of anomalous regions influence the large-scale magnetic field dynamics in diverse ways. We establish that the results of our numerical study are consistent with the algebraic (analytic) approach to explaining the Sun's dipole moment evolution. Our results are relevant for understanding how anomalous active regions modulate the Sun's large-scale dipole moment buildup and its reversal timing within the framework of the Babcock–Leighton dynamo mechanism—now believed to be the primary source of solar cycle variations.

Journal Article Type Article
Acceptance Date May 15, 2023
Online Publication Date Aug 1, 2023
Publication Date Aug 10, 2023
Deposit Date Oct 25, 2023
Publicly Available Date Oct 25, 2023
Journal The Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 953
Issue 1
Article Number 51
Keywords Space and Planetary Science; Astronomy and Astrophysics
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Copyright Statement
© 2023. The Author(s). Published by the American Astronomical Society.
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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