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  Extreme-UV quiet Sun brightenings observed by the Solar Orbiter/EUI

Berghmans, D., Auchère, F., Long, D. M., Soubrié, E., Mierla, M., Zhukov, A. N., et al. (2021). Extreme-UV quiet Sun brightenings observed by the Solar Orbiter/EUI. Astronomy and Astrophysics, 656: L4. doi:10.1051/0004-6361/202140380.

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Berghmans, D., Author
Auchère, F., Author
Long, D. M., Author
Soubrié, E., Author
Mierla, M., Author
Zhukov, A. N., Author
Schühle, Udo1, Author              
Antolin, P., Author
Harra, L., Author
Parenti, S., Author
Podladchikova, O., Author
Aznar Cuadrado, Regina1, Author              
Buchlin, É., Author
Dolla, L., Author
Verbeeck, C., Author
Gissot, S., Author
Teriaca, Luca1, Author              
Haberreiter, M., Author
Katsiyannis, A. C., Author
Rodriguez, L., Author
Kraaikamp, E., AuthorSmith, P.J., AuthorStegen, K., AuthorRochus, P., AuthorHalain, J. P., AuthorJacques, L., AuthorThompson, W. T., AuthorInhester, Bernd1, Author               more..
Affiliations:
1Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              

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Free keywords: Sun: UV radiation / Sun: transition region / Sun: corona / instrumentation: high angular resolution
 Abstract: Context. The heating of the solar corona by small heating events requires an increasing number of such events at progressively smaller scales, with the bulk of the heating occurring at scales that are currently unresolved. Aims. The goal of this work is to study the smallest brightening events observed in the extreme-UV quiet Sun. Methods. We used commissioning data taken by the Extreme Ultraviolet Imager (EUI) on board the recently launched Solar Orbiter mission. On 30 May 2020, the EUI was situated at 0.556 AU from the Sun. Its High Resolution EUV telescope (HRIEUV, 17.4 nm passband) reached an exceptionally high two-pixel spatial resolution of 400 km. The size and duration of small-scale structures was determined by the HRIEUV data, while their height was estimated from triangulation with simultaneous images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory mission. This is the first stereoscopy of small-scale brightenings at high resolution. Results. We observed small localised brightenings, also known as ‘campfires’, in a quiet Sun region with length scales between 400 km and 4000 km and durations between 10 s and 200 s. The smallest and weakest of these HRIEUV brightenings have not been previously observed. Simultaneous observations from the EUI High-resolution Lyman-α telescope (HRILya) do not show localised brightening events, but the locations of the HRIEUV events clearly correspond to the chromospheric network. Comparisons with simultaneous AIA images shows that most events can also be identified in the 17.1 nm, 19.3 nm, 21.1 nm, and 30.4 nm pass-bands of AIA, although they appear weaker and blurred. Our differential emission measure analysis indicated coronal temperatures peaking at log T ≈ 6.1 − 6.15. We determined the height for a few of these campfires to be between 1000 and 5000 km above the photosphere. Conclusions. We find that ‘campfires’ are mostly coronal in nature and rooted in the magnetic flux concentrations of the chromospheric network. We interpret these events as a new extension to the flare-microflare-nanoflare family. Given their low height, the EUI ‘campfires’ could stand as a new element of the fine structure of the transition region-low corona, that is, as apexes of small-scale loops that undergo internal heating all the way up to coronal temperatures.

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Language(s): eng - English
 Dates: 2021
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1051/0004-6361/202140380
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
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Affiliations:
Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: - Volume / Issue: 656 Sequence Number: L4 Start / End Page: - Identifier: ISSN: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1