Automating Ellerman bomb detection in ultraviolet continua

Abstract

Ellerman bombs are transient brightenings in the wings of H-alpha 6563 Å that pinpoint photospheric sites of magnetic reconnection in solar active regions. Their partial visibility in the 1600 Å and 1700 Å continua registered routinely by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) offers a unique opportunity to inventory such magnetic-field disruptions throughout the AIA database if a reliable recipe for their detection can be formulated. This is done here. We improve and apply an H-alpha Ellerman bomb detection code to ten data sets spanning viewing angles from solar disc centre to the limb. They combine high-quality H-alpha imaging spectroscopy from the Swedish 1-m Solar Telescope with simultaneous AIA imaging around 1600 Å and 1700 Å. A trial grid of brightness, lifetime and area constraints is imposed on the AIA images to define optimal recovery of the 1735 Ellerman bombs detected in H-alpha. The best results when optimising simultaneously for recovery fraction and reliability are obtained from 1700 Å images by requiring 5-sigma brightening above the average 1700 Å nearby quiet-Sun intensity, lifetime above one minute, area of 1-18 AIA pixels. With this recipe 27% of the AIA detections are H-alpha-detected Ellerman bombs while it recovers 19% of these (of which many are smaller than the AIA resolution). Better yet, among the top 10% AIA 1700 Å detections selected with combined brightness, lifetime and area thresholds as many as 80% are H-alpha Ellerman bombs. Automated selection of the best 1700 Å candidates therefore opens the entire AIA database for detecting most of the more significant photospheric reconnection events. This proxy is applicable as flux-dynamics tell-tale in studying any Earth-side solar active region since early 2010 up to the present.

Accepted for publication in Astronomy & Astrophysics. 16 pages, 11 figures

References in corpus (9)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• Hot Explosions in the Cool Atmosphere of the Sun
• CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter
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• Small-Scale Structuring Of Ellerman Bombs at Solar Limb
• Statistical Analysis of Small Ellerman Bomb Events
• Various Local Heating Events in the Earliest Phase of Flux Emergence
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Cited by in corpus (3)

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• Signatures of ubiquitous magnetic reconnection in the lower solar atmosphere
• The multi-thermal chromosphere: inversions of ALMA and IRIS data