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arXiv · 2401.12077

Observations of magnetic reconnection in the deep solar atmosphere in the H-epsilon line

L. Rouppe van der Voort·J. Joshi·K. Krikova
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Abstract

Magnetic reconnection in the deep solar atmosphere can give rise to enhanced emission in the Balmer hydrogen lines, a phenomenon known as Ellerman bombs (EBs). It is most common to observe EBs in the H-alpha and H-beta lines. High quality shorter wavelength Balmer line observations of EBs are rare but have the potential to provide the most highly resolved view on reconnection. We evaluate the H-epsilon 3970 A line as an EB diagnostic by analyzing high quality observations in different Balmer lines. Observations of different targets and viewing angles were acquired with the Swedish 1-m Solar Telescope. These observations sample EBs in different environments: active regions, quiet Sun, and the penumbra and moat of a sunspot. We employed an automated detection method for quiet Sun EBs based on k-means clustering. Ellerman bombs in the H-epsilon line show similar characteristics as in the longer wavelength Balmer lines: enhanced intensity as compared to the surroundings, rapid variability, and flame-like morphology. In a 24 min quiet Sun time series, we detected 1674 EBs in the H-epsilon line which is 1.7 times more than in H-beta. The quiet Sun EBs measured in H-epsilon are very similar as in H-beta: they have similar lifetimes, area, brightness, and spatial distribution. Most of the EBs detected in H-epsilon are closer to the limb than their H-beta counterparts. This can be explained by the H-epsilon line core EB emission being formed higher in the atmosphere than the H-beta EB wing emission. We conclude that the H-epsilon line is well suited for studying EBs and consequently probes the dynamics of magnetic reconnection in the solar atmosphere at the smallest scales. Our findings suggests that the deep atmosphere in the quiet Sun may host more than 750,000 reconnection events with EB signature at any time. That is significantly more than what was found in earlier H-beta observations.

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L. Rouppe van der Voort, J. Joshi, K. Krikova. 2024-01-22. Observations of magnetic reconnection in the deep solar atmosphere in the H-epsilon line. https://arxiv.org/abs/2401.12077

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