Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI

Alipour, N., Safari, H., Verbeeck, C., Berghmans, D., Auchère, F., Chitta, L. P., Antolin, Patrick, Barczynski, K., Buchlin, É., Aznar Cuadrado, R., Dolla, L., Georgoulis, M. K., Gissot, S., Harra, L., Katsiyannis, A. C., Long, D. M., Mandal, S., Parenti, S., Podladchikova, O., Petrova, E., Soubrié, É., Schühle, U., Schwanitz, C., Teriaca, L., West, M. J. and Zhukov, A. N. (2022) Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI. Astronomy & Astrophysics, 663. A128. ISSN 0004-6361

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Abstract

Context. Accurate detections of frequent small-scale extreme ultraviolet (EUV) brightenings are essential to the investigation of the physical processes heating the corona.

Aims. We detected small-scale brightenings, termed campfires, using their morphological and intensity structures as observed in coronal EUV imaging observations for statistical analysis.

Methods. We applied a method based on Zernike moments and a support vector machine (SVM) classifier to automatically identify and track campfires observed by Solar Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA).

Results. This method detected 8678 campfires (with length scales between 400 km and 4000 km) from a sequence of 50 High Resolution EUV telescope (HRIEUV) 174 E images. From 21 near co-temporal AIA images covering the same field of view as EUI, we found 1131 campfires, 58% of which were also detected in HRIEUV images. In contrast, about 16% of campfires recognized in HRIEUV were detected by AIA. We obtain a campfire birthrate of 2 E-10 16m 2s 1. About 40% of campfires show a duration longer than 5 s, having been observed in at least two HRIEUV images. We find that 27% of campfires were found in coronal bright points and the remaining 73% have occurred out of coronal bright points. We detected 23 EUI campfires with a duration greater than 245 s. We found that about 80% of campfires are formed at supergranular boundaries, and the features with the highest total intensities are generated at network junctions and intense H I Lyman-α emission regions observed by EUI/HRILya. The probability distribution functions for the total intensity, peak intensity, and projected area of campfires follow a power law behavior with absolute indices between 2 and 3. This self-similar behavior is a possible signature of self-organization, or even self-organized criticality, in the campfire formation process.

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