Ly α Emission Enhancement Associated with Soft X-Ray Microflares

作者：Zhengyuan Tian, Feng Li, Lei Lu, Fanxiaoyu Xia, Yang Su, Wei-Qun Gan, Hui Li, Yue Zhou · 发表于：Research in Astronomy and Astrophysics · 年份：2023 · DOI：10.1088/1674-4527/accc75 · 被引用次数：2 · 研究领域：Solar and Space Plasma Dynamics、Solar Radiation and Photovoltaics、Atmospheric Ozone and Climate

Abstract Ly α (Ly α , 1216 Å) is the strongest emission line in the solar ultraviolet spectrum. In the present work, we obtained a Ly α enhancement catalog covering flares larger than B1 class from the GOES/EUVS data during 2010–2016. We focused on the 242 B-class events which are less investigated, however, show non-negligible Ly α emission enhancement. We found that on average the Ly α peak of B-class flares is 0.85% stronger than the background. For the flare energetics, it is found that the weaker the soft X-ray (SXR) flare, the larger the ratio of the radiated energy in Ly α to SXR. Using the RHESSI data and multi-wavelength observations taken by SDO-AIA, we diagnose the thermal and non-thermal properties of several flares. Three case studies show that the coincidence of the Ly α peak with the SXR time-derivative peak is not a sufficient condition of the nonthermal property of a Ly α microflare. The Ly α enhancement in the microflares may be caused by the nonthermal electron beams or/and thermal conduction. However for type III events, we found that the delay of the Ly α peak with respect to the SXR peak can be attributed to either the Ly α emission from a filament erupted or the cooling of the thermal plasma in flare loops. Furthermore, interestingly the Ly α emission from filaments can not only occur in the decay phase of the flare, but also in the pre-flare phase. In this case, the Ly α emission was originated from an erupted filament which probably initiated the flar...