反冲先导始发过程高分辨率光电同步观测与研究

The excitation of recoil leader is one of the key problems in lightning physics. However, there is a lack of systematic observation data due to the great spatial and temporal randomness of the origination of recoil leader, high transmission speed and low resolution of previous observation equipment, we have not understood clearly about the characteristics and physical mechanisms of the originating process of recoil leader. Based on the existing Guangzhou lightning observation platform, this project will use multiple high frame rate cameras and sub-microsecond VHF broadband interferometers to perform comprehensive observation and research on the high- spatiotemporal resolution optical 2D/3D and 2D/3D location of the radiation source during the originating process of recoil leader. Give full play to the observation advantages of the two systems and integrating the waveform of electromagnetic field, the synchronous observation data of recoil leader, including optical, the location of radiation source and the change of electromagnetic field, will be obtained. The 2D (statistical)/3D (cases) fine characteristics of originating process of recoil leader will be analyzed. Breaking through the limitation of isolated analyzing the recoil leader only in before, the possible correlation between the fast positive breakdown and the excitation of recoil leader will be researched in K process. This research of this project will deepen our scientific knowledge of the characteristics and mechanism of the recoil leader and the connection between the different discharge processes in lightning flash.

反冲先导的激发是雷电物理学研究的焦点问题之一，但由于该过程的时空随机性大、传输速度快，加上以往观测设备的分辨率较低，使得对于反冲先导始发过程依然缺乏系统性的高分辨率观测资料，导致对反冲先导始发特征和物理机制的认识还不够清晰。本项目拟基于已有的广州雷电观测试验平台，利用多台高帧率摄像机和亚微秒量级甚高频宽带干涉仪对反冲先导始发过程开展高时空分辨率光学二维/三维和辐射源二维/三维定位综合观测与研究。发挥两种系统的观测优势，并结合地面电磁场变化的观测，获取反冲先导光学、辐射源定位和电磁场同步观测资料，分析反冲先导始发的二维（统计）/三维（个例）精细特征，同时突破之前只孤立地分析反冲先导的局限，探讨K过程中快速正击穿与反冲先导的激发之间可能存在的联系。本项目将深化人们对反冲先导始发特征、机理以及不同放电过程之间的联系等方面的科学认识。

雷电研究中一个悬而未决的焦点问题是如何解释发生在分叉的正先导通道中或多回击负地闪回击间或回击后的反冲先导现象。广州雷电综合观测试验平台同时具备高时空分辨率光学观测和辐射源定位观测能力，为我们针对反冲先导始发过程开展光学和定位同步观测和研究，观测并积累丰富的反冲先导数据成为可能。. 本项目在前期雷电观测试验的基础上，新增了2个观测点，将广州雷电综合观测站点扩容至6个，显著提升了闪电的综合观测能力，同时设计了针对反冲先导的新观测方案，实现了反冲先导高时空分辨率光学和高精度、高灵敏度辐射源定位同步观测，通过近三年的观测试验，获得了丰富的适合分析反冲先导始发特征的雷电观测数据。. 基于广州雷电观测站获取的高速摄像和电场变化同步资料，分析了上行闪电中反冲先导的始发和传输的细节特征。发现双向直窜/反冲先导的负端沿着上行正先导的已冷却的分叉通道传输，最终到达塔顶引发回击。对双向反冲先导序列的正端接地引发的正地闪回击过程进行了详细分析，发现连续发生的双向反冲先导负端与上方通道连接后，形成的新正极性分叉通道演变为朝地面自持发展的正先导，并最终与地面连接产生正回击。.对反冲先导与快速正击穿过程之间的关联性进行了分析，发现双向发展的反冲先导正端在回击前、后突然延展（快速正击穿）现象可能会出现多次，突然延展现象有时由双向反冲先导的正端与已有的悬空先导序列相连而引发；对在一次单回击正地闪中观测到针状结构的始发和传输特征进行了详细分析，发现针状结构的闪烁是沿着针通道发展的反冲流光过程。回击后期和连续电流阶段大量负电荷从正先导通道热芯进入附近的正极性电晕鞘并径向运动激活了针。. 本研究充分发挥了广州雷电综合观测站具备的高时空分辨率光学和辐射源定位同步观测优势，提升了我们在反冲先导始发特征和机理以及不同放电过程之间相关性等方面的科学认识，深化了我们对雷电物理过程的理解。