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arXiv · 2608.30812

Study of Butterfly-Shaped Coronal Hole Evolution Across the Solar Disk

Bhairab Ale·Khagendra Katuwal·Shiv Narayan Yadav
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Abstract

We studied the evolution of a butterfly-shaped coronal hole (CH) observed from 2025 September 8 to 14 using SDO/AIA 193~\AA\ images and SDO/HMI line-of-sight magnetograms. The CH boundary was identified using a fixed 100~DN intensity threshold, and its area, mean EUV intensity, and total unsigned magnetic flux were tracked across the solar disk. As the CH approached the central meridian, its area increased from approximately $7.70\times10^{16}$ to $1.63\times10^{17}$~m$^{2}$ and its unsigned magnetic flux from $8.68\times10^{21}$ to $1.91\times10^{22}$~Mx, while the mean 193~\AA\ intensity decreased from about 61 to 45~DN. The area and unsigned flux showed similar temporal trends, whereas the intensity varied oppositely. Near central-meridian passage, these quantities remained relatively stable for several days. A high-speed solar-wind stream was detected at 1~AU about 2--4 days later, reaching 600--750~km~s$^{-1}$, consistent with the CH being its likely solar source. These results link the morphological, radiative, and magnetic evolution of the CH with the subsequent high-speed solar-wind stream.

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Bhairab Ale, Khagendra Katuwal, Shiv Narayan Yadav. 2026-08-31. Study of Butterfly-Shaped Coronal Hole Evolution Across the Solar Disk. https://arxiv.org/abs/2608.30812

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