On April 18, The Astrophysical Journal published the latest work, conducted by Dr. YE Jing from Yunnan Observatories (Corresponding author) and Dr. CAI Qiangwei from Luoyang Normal University, on the thermodynamics of the Supra-Arcade Fans (SAFs). Both observational and numerical results imply that there might exist a compressed interface in the SAF, where plasma environment shows a remarkable change in density, temperature and turbulence.

It is well known that a distributed and hot structure named as supra-arcade fan exists above post-flare loops during the solar eruption. The location of the SAF is spatially consistent with various emission sources. However, the plasma evolution features in the SAF and the origin of the hard X-ray source are still poorly understood.

Based on observations from the Interface Region Imaging Spectrograph and Hinode for the 2017 September 10 flare, researchers found that the SAF presents discontinuous characters during the rising process, which indicate a nonuniform magnetic reconnection process. Additionally, the temperature and density increase spatially at the upper boundary of the SAF, which implies that a compressed interface may exist in the SAF.

With the help of numerical experiments and synthetic extreme ultraviolet (EUV) images, researchers conclude that the interface could be related to termination shocks (TSs), of which the height is close to the hard X-ray source. In turn, the variations of the spectral profiles might be useful tools for identifying TSs from EUV spectral observations.

This study provides us both observational and theorical evidences that the interface related to TSs might be detected by EUV observations in the future. (within 10 days)

 Contact:

Jing YE, Yunnan Observatories, CAS

yj@ynao.ac.cn