Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI

Zhukov, A. N., Mierla, M., Auchère, F., Gissot, S., Rodriguez, L., Soubrié, E., Thompson, W. T., Inhester, B., Nicula, B., Antolin, Patrick, Parenti, S., Buchlin, É., Barczynski, K., Verbeeck, C., Kraaikamp, E., Smith, P. J., Stegen, K., Dolla, L., Harra, L., Long, D. M., Schühle, U., Podladchikova, O., Aznar Cuadrado, R., Teriaca, L., Haberreiter, M., Katsiyannis, A. C., Rochus, P., Halain, J.-P., Jacques, L. and Berghmans, D. (2021) Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI. Astronomy & Astrophysics, 656. A35. ISSN 0004-6361

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Context. The three-dimensional fine structure of the solar atmosphere is still not fully understood as most of the available observations are taken from a single vantage point.
Aims. The goal of the paper is to study the three-dimensional distribution of the small-scale brightening events ("campfires") discovered in the extreme-UV quiet Sun by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter.
Methods. We used a first commissioning data set acquired by the EUI's High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and we combined it with simultaneous data taken by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171 Å passband. The two-pixel spatial resolution of the two telescopes is 400 km and 880 km, respectively, which is sufficient to identify the campfires in both data sets. The two spacecraft had an angular separation of around 31.5° (essentially in heliographic longitude), which allowed for the three-dimensional reconstruction of the campfire position. These observations represent the first time that stereoscopy was achieved for brightenings at such a small scale. Manual and automatic triangulation methods were used to characterize the campfire data.
Results. The height of the campfires is located between 1000 km and 5000 km above the photosphere and we find a good agreement between the manual and automatic methods. The internal structure of campfires is mostly unresolved by AIA; however, for a particularly large campfire, we were able to triangulate a few pixels, which are all in a narrow range between 2500 and 4500 km.
Conclusions. We conclude that the low height of EUI campfires suggests that they belong to the previously unresolved fine structure of the transition region and low corona of the quiet Sun. They are probably apexes of small-scale dynamic loops heated internally to coronal temperatures. This work demonstrates that high-resolution stereoscopy of structures in the solar atmosphere has become feasible.

Item Type: Article
Additional Information: Funding Information: A.N.Z. dedicates this work to the memory of his teacher and mentor, Igor S. Veselovsky (1940–2020), who was an ardent proponent of studies of the coronal fine structure. Solar Orbiter is a space mission of international collaboration between ESA and NASA, operated by ESA. The EUI instrument was built by CSL, IAS, MPS, MSSL/UCL, PMOD/WRC, ROB, LCF/IO with funding from the Belgian Federal Science Policy Office (BELPSO); the Centre National d’Etudes Spatiales (CNES); the UK Space Agency (UKSA); the Bundesministerium für Wirtschaft und Energie (BMWi) through the Deutsches Zentrum für Luft-und Raumfahrt (DLR); and the Swiss Space Office (SSO). The ROB team thanks the Belgian Federal Science Policy Office (BELSPO) for the provision of financial support in the framework of the PRODEX Programme of the European Space Agency (ESA) under contract numbers 4000112292, 4000117262, and 4000134474. PA and DML acknowledge funding from STFC Ernest Rutherford Fellowships No. ST/R004285/2 and ST/R003246/1, respectively. SP acknowledges the funding by CNES through the MEDOC data and operations center. LH and KB are grateful to the SNF for the funding of the project number 200021_188390.
Uncontrolled Keywords: Sun: UV radiation, Sun: transition region, Sun: corona, Techniques: high angular resolution
Subjects: F300 Physics
F500 Astronomy
Department: Faculties > Engineering and Environment > Mathematics, Physics and Electrical Engineering
Depositing User: John Coen
Date Deposited: 14 Jan 2022 12:32
Last Modified: 14 Jan 2022 12:45

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