Diagnostics of Ellerman bombs with high-resolution spectral data  

作　　者：Zhen Li Cheng Fang Yang Guo Peng-Fei Chen Zhi Xu Wen-Da Cao 

机构地区：[1]School of Astronomy and Space Science, Nanjing University [2]Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education [3]Collaborative Innovation Center of Modern Astronomy and Space Exploration [4]Yunnan Observatories, Chinese Academy of Sciences [5]Big Bear Solar Observatory, New Jersey Institute of Technology

出　　处：《Research in Astronomy and Astrophysics》2015年第9期1513-1524,共12页天文和天体物理学研究（英文版）

基　　金：supported by the National Natural Science Foundation of China (NSFC, Grants 10878002, 10933003, 11025314, 10673004, 11203014 and 11103075);NKBRSF (Grant Nos. 2011CB811402 and 2014CB744203);the support of the US NSF (AGS0847126 and AGS-1250818);NASA (NNX13AG14G)

摘　　要：Ellerman bombs （EBs） are tiny brightenings often observed near sunspots. The most impressive characteristic of EB spectra is the two emission bumps in both wings of the Hα and Ca II 8542 A lines. High-resolution spectral data of three small EBs were obtained on 2013 June 6 with the largest solar telescope, the 1.6 m New Solar Telescope at the Big Bear Solar Observatory. The characteristics of these EBs are analyzed. The sizes of the EBs are in the range of 0.3＂ - 0.8＂ and their durations are only 3-5 min. Our semi-empirical atmospheric models indicate that the heating occurs around the temperature minimum region with a temperature increase of 2700- 3000 K, which is surprisingly higher than previously thought. The radiative and kinetic energies are estimated to be as high as 5 × 1025 - 3.0 × 10^26 erg despite the small size of these EBs. Observations of the magnetic field show that the EBs just appeared in a parasitic region with mixed polarities and were accompanied by mass motions. Nonlinear force-free field extrapolation reveals that the three EBs are connected with a series of magnetic field lines associated with bald patches, which strongly implies that these EBs should be produced by magnetic reconnection in the solar lower atmosphere. According to the lightcurves and the estimated magnetic reconnection rate, we propose that there is a three phase process in EBs： pre-heating, flaring and cooling phases.Ellerman bombs （EBs） are tiny brightenings often observed near sunspots. The most impressive characteristic of EB spectra is the two emission bumps in both wings of the Hα and Ca II 8542 A lines. High-resolution spectral data of three small EBs were obtained on 2013 June 6 with the largest solar telescope, the 1.6 m New Solar Telescope at the Big Bear Solar Observatory. The characteristics of these EBs are analyzed. The sizes of the EBs are in the range of 0.3＂ - 0.8＂ and their durations are only 3-5 min. Our semi-empirical atmospheric models indicate that the heating occurs around the temperature minimum region with a temperature increase of 2700- 3000 K, which is surprisingly higher than previously thought. The radiative and kinetic energies are estimated to be as high as 5 × 1025 - 3.0 × 10^26 erg despite the small size of these EBs. Observations of the magnetic field show that the EBs just appeared in a parasitic region with mixed polarities and were accompanied by mass motions. Nonlinear force-free field extrapolation reveals that the three EBs are connected with a series of magnetic field lines associated with bald patches, which strongly implies that these EBs should be produced by magnetic reconnection in the solar lower atmosphere. According to the lightcurves and the estimated magnetic reconnection rate, we propose that there is a three phase process in EBs： pre-heating, flaring and cooling phases.

关 键 词：Sun： chromosphere -- Sun： photosphere -- line profiles -- magnetic reconnection 

分 类 号：P111.41[天文地球—天文学]