Study of temporal evolution of emission spectrum in a steeply rising submillimeter burst

作     者：Jian-Ping Li Ai-Hua Zhou Xin-Dong Wang 

作者机构：Key Laboratory of Dark Matter and Space Astronomy Chinese Academy of Sciences Nanjing 210008 China Purple Mountain Observatory Chinese Academy of Sciences Nanjing 210008 China School of Public Administration Hohai University Nanjing 210098 China 

出 版 物：《Research in Astronomy and Astrophysics》 (天文和天体物理学研究（英文版）)

年 卷 期：2016年第16卷第1期

页      面：67-72页

核心收录：

学科分类：07[理学] 070401[理学-天体物理] 0704[理学-天文学] 

基　　金：supported by the National Natural Science Foundation of China (Grant No.11333009) the National Basic Research Program of China (973 program,2014CB744200) 

主　　题：Sun: submillimeter burst    Sun: energetic electrons    Sun: radio source size 

摘      要：The temporal evolution of a spectrum during a steeply rising submillimeter（THz） burst that occurred on 2003 November 2 was investigated in detail for the first *** show that the flux density of the THz spectrum increased steeply with frequency above 200 *** average rising rates reached a value of 235 sfu GHz^（-1）（corresponding to spectral index α of 4.8） during the *** flux densities reached about 4 000 and 70 000 sfu at 212 and 405 GHz at the maximum phase,*** emissions at 405 GHz maintained such a continuous high level that they largely exceeded the peak values of the microwave（MW） spectra during the main *** studies suggest that only energetic electrons with a low-energy cutoff of~ 1 MeV and number density of ~ 10~6-10~8 cm^（-3） can produce such a strong and steeply rising THz component via gyrosynchrotron radiation based on numerical simulations of burst spectra in the case of a nonuniform magnetic *** electron number density N,derived from our numerical fits to the THz temporal evolution spectra,increased substantially from 8 ×10~6 to 4 × 10~8 cm^（-3）,i.e.,the N value increased 50 times during the rise *** the decay phase it decreased to 7 ×10~7 cm^（-3）,i.e.,it decreased by about five times from the maximum *** total electron number decreased an order of magnitude from the maximum phase to the decay ***,the variation in amplitude of N is only about one time in the MW emission source during this burst,and the total electron number did not decrease but increased by about 20%during the decay ***,we find that the THz source radius decreased by about 24%while the MW source radius,on the contrary,increased by 28%during the decay phase.