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arXiv · 2504.15996

Small-scale dynamic phenomena associated with interacting fan-spine topologies: quiet-Sun Ellerman bombs, UV brightenings, and chromospheric inverted-Y-shaped jets

Aditi Bhatnagar·Avijeet Prasad·Daniel Nóbrega-Siverio·Luc Rouppe van der Voort·Jayant Joshi
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Abstract

QSEBs are small-scale magnetic reconnection events in lower solar atmosphere. Sometimes, they exhibit transition region counterparts, known as UV brightenings. Magnetic field extrapolations suggest that QSEBs can occur at various locations of a fan-spine topology, with UV brightening occurring at null point through a common reconnection process. We aim to understand how complex magnetic configurations like interacting fan-spine topologies can cause small-scale dynamic phenomena in lower atmosphere. QSEBs were detected using k-means clustering on Hbeta observations from Swedish 1-m Solar Telescope (SST). Further, chromospheric inverted-Y-shaped jets were identified in the Hbeta blue wing. Magnetic field topologies were determined through potential field extrapolations from photospheric magnetograms using the Fe I 6173 A line. UV brightenings were detected in IRIS 1400 A SJI. We identify two distinct magnetic configurations associated with QSEBs, UV brightenings, and chromospheric inverted-Y-shaped jets. The first involves a nested fan-spine structure where, due to flux emergence, an inner 3D null forms inside fan surface of an outer 3D null with some overlap. QSEBs occur at two footpoints along the shared fan surface, with UV brightening located near the outer 3D null point. The jet originates close to the two QSEBs and follows the path of high squashing factor Q. We discuss a comparable scenario using a numerical simulation. In second case, two adjacent fan-spine topologies share fan footpoints at a common positive polarity patch, with the QSEB, along with a chromospheric inverted-Y-shaped jet, occurring at the intersection having high Q values. This study demonstrates through observational and modelling support that associated QSEBs, UV brightenings, and chromospheric inverted-Y-shaped jets share a common origin driven by magnetic reconnection between interacting fan-spine topologies.

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Aditi Bhatnagar, Avijeet Prasad, Daniel Nóbrega-Siverio, Luc Rouppe van der Voort, Jayant Joshi. 2025-04-29. Small-scale dynamic phenomena associated with interacting fan-spine topologies: quiet-Sun Ellerman bombs, UV brightenings, and chromospheric inverted-Y-shaped jets. https://doi.org/10.1051/0004-6361%2F202453344

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