中文摘要：

利用闪电VHF辐射源短基线定位系统2009年东北大兴安岭地区的观测资料,对正、负地闪和云闪放电过程中的VHF辐射源进行了定位研究.根据闪电VHF辐射源的二维位置（方位角和仰角）随时间的演变特征,结合同步观测的快、慢电场变化资料分析发现,持续时间较长的地闪预击穿过程在云中的放电通道呈双层结构,预击穿过程结束阶段的云内放电表现为反冲流光,预击穿过程的平均速度在10~4m/s量级.预击穿过程为梯级先导的发展提供了必要的条件,梯级先导从预击穿起始位置开始并向下发展,产生较强的辐射,平均速度在10~5m/s量级.K过程主要是流光沿之前已电离通道的传输.正、负地闪回击阶段前后的放电特征有明显不同,正地闪回击之后,连续电流期间的较长时间的云内放电产生较强的VHF辐射.对闪电在125—200 MHz频段范围的VHF辐射频谱特征的统计分析发现,辐射能量呈现出幅值随频率增加而减小的趋势,在通带范围上基本遵循f~（-2.9）的衰减率递减.

英文摘要：

A lightning VHF radiation source location system based on short-baseline technology is used to study the location of VHF radiation source in the lightning discharge process.The observation was conducted in Daxing＇anling during summer of 2009.Positive cloud-to-ground（CG） lightning,negative CG lightning,and intra-cloud（IC） lightning are analyzed based on the locating results and simultaneous electric field changes.The long lasting preliminary breakdown process of CG flash appears as two-level structure of discharge channel in cloud.There are obvious recoil streamers during the final stage of preliminary breakdown process.The preliminary breakdown process propagates at a speed of about 10~4 m/s.The preliminary breakdown seems to be necessary for the initiation of stepped leader.The stepped leader starts from the source region of preliminary breakdown and propagates downwards.The stepped leader produces intensive VHF radiation.The propagation speed of stepped leader is about 10~5 m/s.The K process is caused by the streamers propagating backwards and forwards along the electrified channel.Characteristics of discharge processes before and after the return stroke of positive CG flash are different from those of negative CG flash obviously.During long continuing current after the return stroke of positive CG flash,discharges in cloud produce intensive VHF radiation.The energy spectrum of the VHF radiation produced by lightning is studied statistically.It is found that the energy spectrum of VHF radiation decreases quickly with the frequency at a rate of about f~（-2,9） between 125 and 200 MHz.