Narang, N. ; Verbeeck, C. ; Mierla, M. ; Berghmans, D. ; Auchère, F. ; Chitta, L. P. ; Priest, E. ; EUI, Team

published in Solar Orbiter Science Nugget, 06/08/2025 issue #67 (2025)

Abstract: The extreme-ultraviolet (EUV) brightenings identified by Extreme Ultraviolet Imager (EUI) [1] aboard Solar Orbiter [2], commonly known as campfires, are the small-scale transient brightenings detected in the solar corona. The ubiquitous presence of localised transient brightenings throughout the solar atmosphere is generally attributed to an impulsive release of energy by the process of magnetic reconnection [3,4]. In the solar transition region and lower corona, a plethora of small-scale localised brightening events in the quiet Sun, with typical length scales of a few Megameters, has been documented in the literature [5,6]. Despite the detections of a variety of EUV transients in the micro-to-nano-flare energy range, their estimated energy-flux rates have been reported to be insufficient to balance the coronal quiet-Sun energy losses [7,8]. Recently, the EUI/HRIEUV observations of quiet Sun have revealed the presence of new members of the small-scale EUV transient brightenings in the solar corona [9,10]. Commonly known as campfires, these HRIEUV brightenings appear in the lower corona, and above the locations of supergranular network boundaries. They have been reported to have sizes between 0.08 Mm2 and 5 Mm2 and lifetimes between 10 seconds and 200 seconds. These brightenings are proposed to be the newest members of the nanoflare family, and can possibly play significant role in heating the solar corona. In this study [11], we took advantage of the unique EUV observations of the quiet-Sun corona with unprecedented resolution provided by HRIEUV in close proximity to the Sun. These HRIEUV observations have spatial and temporal resolutions about two times better than those used earlier to study the HRIEUV brightenings. With such unique set of observations we perform a statistical study of the properties of smallest-scale HRIEUV brightenings which were previously inaccessible.

Keyword(s): Solar Orbiter ; EUI ; brightenings
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