| Issue |
A&A
Volume 679, November 2023
|
|
|---|---|---|
| Article Number | A9 | |
| Number of page(s) | 9 | |
| Section | The Sun and the Heliosphere | |
| DOI | https://doi.org/10.1051/0004-6361/202346944 | |
| Published online | 30 October 2023 | |
Morphological evidence for nanoflares heating warm loops in the solar corona⋆
1
Yunnan Observatories, Chinese Academy of Sciences, 396 Yangfangwang, Guandu District, Kunming 650216, PR China
e-mail: biyi@ynao.ac.cn; jkf@ynao.ac.cn
2
Yunnan Key Laboratory of Solar Physics and Space Science, 396 Yangfangwang, Guandu District, Kunming 650216, PR China
3
College of Big Data and Intelligent Engineering, Southwest Forestry University, Kunming 650224, PR China
Received:
19
May
2023
Accepted:
8
September
2023
Context. Nanoflares are impulsive energy releases that occur due to magnetic reconnection in the braided coronal magnetic field, which is a potential mechanism for heating the corona. However, there are still sporadic observations of the interchange of braiding structure segments and footpoints inside coronal loops, which is predicted to be the morphological evolution of the reconnecting magnetic bundles in the nanoflare picture.
Aims. This work aims to detect the evolutions of the pairs of braiding strands within the apparent single coronal loops observed in Atmospheric Imaging Assembly (AIA) images.
Methods. The loop strands were detected on two kinds of upsampled AIA 193 Å images, which were obtained by upscaling the point spread function matched AIA images via bicubic interpolation and were generated using a super-resolution convolutional neural network. The architecture of the network is designed to map the AIA images to unprecedentedly high spatial resolution coronal images taken by the High-resolution Coronal Imager (Hi-C) during its brief flight.
Results. At times, pairs of separate strands that appear braided together later evolved into pairs of almost parallel strands with completely exchanged parts. These evolutions offer morphological evidence that magnetic reconnections between the braiding strands have taken place, which is further supported by the appearance of transient hot emissions containing significant high-temperature components (T > 5 MK) at the footpoints of the braiding structures.
Conlusions. The brief appearances of the two rearranging strands support the idea that magnetic reconnections have occurred within what appears to be a single AIA loop.
Key words: Sun: corona / Sun: flares / Sun: magnetic fields
Movies associated to Figs. 3, 4, and 5 are available at https://www.aanda.org.
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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