基于硬X射线调制望远镜(HXMT)的地球伽玛闪母体闪电及雷暴特征研究

The energetic radiation (such as hard X-rays and gamma-rays) generated by lightning is the hot research subject of international community on atmospheric electricity, and these phenomena indicate that the lightning activity in troposphere has the potential impact on the near-Earth space environment. Due to the limitation and deficiency of relevant detection techniques, the progress on this subject is relatively slow in China. Based on the Lightning Effects Research Platform (LERP), we will conduct the comprehensive observations coordinated with the Hard X-ray Modulation Telescope (HXMT) in East Asia, and reveal the characteristics of low-frequency magnetic sferics from the parent lightning of terrestrial gamma-ray flashes (TGFs) through three years of measurements. Moreover, by conducting the ground-based observations in the regions with relatively dense lightning activity, such as the artificially triggered lightning experiments in Zhanhua of Shandong Province and Conghua of Guangdong Province, we will combine with the radar reflectivity and cloud-top brightness temperature to further identify the physical connection between TGFs and energetic intra-cloud (IC) pulses during the initial stage of IC flashes and the characteristics of parent thunderstorm development. On this basis, we will carry out the low-frequency three-dimensional mapping observation and ground-based electrostatic field measurement with respect to the IC processes with general feature of TGFs, and establish the charge transfer model related to TGFs by means of fitting the charge source. These efforts will help to deeply analyze the physical process involved in the impulsive charge transfer during the initial stage of IC flashes, and better understand the mechanism for the generation of energetic radiation by lightning leaders.

闪电产生的硬X射线及伽玛射线等高能辐射是国际大气电学研究中的热点问题，这些现象表明对流层中的闪电活动对临近空间安全存在潜在影响。由于自主研发相关探测技术的限制，目前国内在这方面的研究进展缓慢。基于初步建成的闪电近地空间效应研究平台，本项目将配合硬X射线调制望远镜卫星（HXMT）在东亚地区开展综合观测，通过三年的综合数据积累，揭示地球伽玛闪（TGF）母体闪电的低频磁场信号特征。此外，通过在中国大陆闪电活动较密集地区开展加密地基观测（如山东沾化、广东从化人工引雷实验基地），结合雷达反射率资料和云顶亮温观测资料，进一步认识TGF同云闪初始阶段大脉冲事件之间的物理相关性和母体雷暴发展特征。在此基础上，开展具有TGF普遍特征的云闪过程的低频三维成像观测和地面静电场测量，通过电荷源拟合的方法建立TGF相关的电荷传输模型，深入分析云闪初始阶段脉冲电荷传输的物理过程并了解闪电先导产生高能辐射的机制。

基于初步建成的闪电近地空间效应研究平台，尤其是2020年起在合肥和广州建设的两套低频/甚低频雷电磁场连续记录设备，本项目配合硬X射线调制望远镜卫星（HXMT）在东亚地区开展综合观测。通过三年的综合数据积累，课题组获得了大量协同观测数据揭示地球伽玛闪（TGF）母体闪电的低频磁场信号特征。观测数据有很大一部分是通过在赤道地区马六甲获得的数据，因此分析结果有很强的地区特色。针对历史观测数据和项目研究期间综合观测数据集，结合雷达反射率资料和云顶亮温观测资料，进一步认识TGF同云闪初始阶段大脉冲事件之间的物理相关性和母体雷暴发展特征，揭示了一类新的TGF产生机制，即TGF主要由雷暴云内大尺度的背景强电场作用产生，不需要闪电放电过程，支持逃逸击穿正反馈机制。与此同时，课题组在山东沾化开展低频三维成像观测，并同其他团队合作在广州从化地区地面静电场组网测量，通过电荷源拟合的方法建立TGF相关的电荷传输模型，深入分析云闪初始阶段脉冲电荷传输的物理过程并了解闪电先导产生高能辐射的机制。项目研制过程中，课题组还分析了深对流雷暴云顶蓝色发光过程相关的云内放电特征及其特殊形态的电磁信号。