Ultraviolet emission of unipolar active regions and a relation between its intensity and magnetic flux decay rate

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Published: Mar 22, 2025
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Keywords:
Sun active regions magnetic flux decay transition layer

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Andrey Plotnikov
Crimean Astrophysical Observatory, Nauchny 298409

Abstract

This study uses data on 617 active regions (ARs) acquired by the Solar Dynamics Observatory. Unipolar ARs exhibit a lower density of He II 304 Å ultraviolet (UV) emission above sunspots as compared to the ARs of other types. Bipolar and multipolar ARs, regardless of their magnetic flux, show a similar density of UV emission above sunspots. In contrast, in unipolar ARs, the UV emission density increases with increasing magnetic flux. This relationship can be used to estimate the magnetic flux values from the maps of UV emission density. Additionally, the total unsigned magnetic flux decay rate is in moderate correlation with the UV emission above sunspots. This correlation may help to explain the phenomenon of slow-decaying unipolar ARs.

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How to Cite
Plotnikov A., 2025. Acta Astrophysica Taurica, vol. 6, no. 1, pp. 5–8. Available at: https://astrophysicatauricum.org/index.php/aat/article/view/102 (Accessed: 29 March 2025)
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Vol. 6 No. 1 (2025)
Section
Research articles
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