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  Extreme-ultraviolet bursts and nanoflares in the quiet-Sun transition region and corona

Chitta, L. P., Peter, H., & Young, P. (2021). Extreme-ultraviolet bursts and nanoflares in the quiet-Sun transition region and corona. Astronomy and Astrophysics, 647: A159. doi:10.1051/0004-6361/202039969.

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 Creators:
Chitta, L. P.1, Author              
Peter, Hardi1, Author              
Young, P.R., Author
Affiliations:
1Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              

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Free keywords: Sun: atmosphere / Sun: corona / Sun: magnetic fields / Sun: transition region / Sun: UV radiation / magnetic reconnection
 Abstract: The quiet solar corona consists of myriads of loop-like features, with magnetic fields originating from network and internetwork regions on the solar surface. The continuous interaction between these different magnetic patches leads to transient brightenings or bursts that might contribute to the heating of the solar atmosphere. The literature on a variety of such burst phenomena in the solar atmosphere is rich. However, it remains unclear whether such transients, which are mostly observed in the extreme ultraviolet (EUV), play a significant role in atmospheric heating. We revisit the open question of these bursts as a prelude to the new high-resolution EUV imagery expected from the recently launched Solar Orbiter. We use EUV image sequences recorded by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) to investigate statistical properties of the bursts. We detect the bursts in the 171 Å filter images of AIA in an automated way through a pixel-wise analysis by imposing different intensity thresholds. By exploiting the high cadence (12 s) of the AIA observations, we find that the distribution of lifetimes of these events peaks at about 120 s. However, a significant number of events also have lifetimes shorter than 60 s. The sizes of the detected bursts are limited by the spatial resolution, which indicates that a larger number of events might be hidden in the AIA data. We estimate that about 100 new bursts appear per second on the whole Sun. The detected bursts have nanoflare-like energies of 1024 erg per event. Based on this, we estimate that at least 100 times more events of a similar nature would be required to account for the energy that is required to heat the corona. When AIA observations are considered alone, the EUV bursts discussed here therefore play no significant role in the coronal heating of the quiet Sun. If the coronal heating of the quiet Sun is mainly bursty, then the high-resolution EUV observations from Solar Orbiter may be able to reduce the deficit in the number of EUV bursts seen with SDO/AIA at least partly by detecting more such events.

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Language(s): eng - English
 Dates: 2021
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: - Volume / Issue: 647 Sequence Number: A159 Start / End Page: - Identifier: ISSN: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1