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arXiv · 2608.26315

Active nests at solar maximum: How nested flux emergence dominated flaring activity and structured the heliosphere

Adam J. Finley·Allan Sacha Brun·Antoine Strugarek·Barbara Perri·Daniel Müller·Miho Janvier·Andy S H To·Henrik Eklund
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Abstract

Multi-viewpoint observations from near-Earth satellites and ESA's Solar Orbiter enable a global view of the Sun. This continuous coverage is essential for characterising active nests. We investigated how the formation of active nests during the maximum of solar cycle 25 affected the Sun's flaring activity and large-scale magnetic field. Active nests were identified from their persistent activity in Carrington coordinates. For each nest, we monitored the evolution of their photospheric magnetic field, extreme ultraviolet emission, and associated solar flares. Their impact on the solar corona was explored through potential field source surface extrapolations and coronagraph observations. These results were then compared with in-situ measurements of solar wind speed and magnetic field polarity. During 156 days of global monitoring in 2024, nearly 80% of all solar flares originated from three active nests in the southern hemisphere. Two of the nests converged over several months, colliding with a burst of activity in October 2024. The third nest was linked to the emergence of NOAA active region AR13664 in May 2024. Magnetically complex NOAA active regions were more prevalent within active nests. During 2024, 28% of the 147 nested active regions were complex, compared to just 16% of the 181 regions elsewhere. In January 2025, two active nests emerged from the collision site, and a new active nest appeared in the north. This reinforced a tilted dipole topology throughout 2025. Active nests modulated global solar activity in 2024 and shaped the solar corona and wind in 2025. Nearly continuous tracking was used to isolate their flaring and flux emergence rates. Active nest migration was driven by the emergence of magnetic flux, implying a coherent sub-surface origin. By anchoring the coronal magnetic field, active nests created more favourable source regions for solar wind connectivity studies.

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Adam J. Finley, Allan Sacha Brun, Antoine Strugarek, Barbara Perri, Daniel Müller, Miho Janvier, Andy S H To, Henrik Eklund. 2026-08-26. Active nests at solar maximum: How nested flux emergence dominated flaring activity and structured the heliosphere. https://arxiv.org/abs/2608.26315

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