EGU General Assembly 2021
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Formation of solar coronal loops through magnetic reconnection in an emerging active region

Zhenyong Hou1, Hui Tian1,2, Hechao Chen1, Xiaoshuai Zhu2, Jiansen He1, Xianyong Bai2, Zhenghua Huang3, and Lidong Xia3
Zhenyong Hou et al.
  • 1School of Earth and Space Sciences, Peking University, Beijing, 100871, China
  • 2Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, China
  • 3Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, Weihai, 264209 Shandong, People’s Republic of China

Coronal loops are building blocks of solar active regions (ARs). However, their formation is not well understood. Here we present direct observational evidence for the formation of coronal loops through magnetic reconnection as new magnetic fluxes emerge to the solar atmosphere. Observations in the EUV passbands of SDO/AIA clearly show the newly formed loops following magnetic reconnection within a vertical current sheet. Formation of the loops is also seen in the Hα images taken by NVST. The SDO/HMI observations show that a positive-polarity flux concentration moves toward a negative-polarity one with a speed of ~0.5 km s-1 before the apparent formation of coronal loops. During the formation of coronal loops, we found signatures of flux cancellation and subsequent enhancement of the transverse field between the two polarities. We have reconstructed the three-dimensional magnetic field structure through a magnetohydrostatic model, which shows field lines consistent with the loops in AIA images. Numerous bright blobs with a width of ~1.5 Mm appear intermittently in the current sheet and move upward with apparent velocities of ~80 km s-1. We have also identified plasma blobs moving to the footpoints of the newly formed large loops, with apparent velocities ranging from 30 to 50 km s-1. A differential emission measure analysis shows that the temperature, emission measure and density of the bright blobs are 2.5-3.5 MK, 1.1-2.3×1028 cm-5 and 8.9-12.9×109 cm-3, respectively. Power spectral analysis of these blobs indicates that the magnetic reconnection is inconsistent with the turbulent reconnection scenario.

How to cite: Hou, Z., Tian, H., Chen, H., Zhu, X., He, J., Bai, X., Huang, Z., and Xia, L.: Formation of solar coronal loops through magnetic reconnection in an emerging active region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1013,, 2021.

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