地面电晕离子对空中引雷始发过程的影响

利用已建立的“地面电晕离子的演化模式”对甘肃省平凉地区一次雷暴过程的空中电荷密度和环境电场的演化情况进行了模拟，发现地面尖端产生的电晕离子如果不被俘获便可在１ｍｉｎ左右内到达５００ｍ的高度上。对空中引雷火箭发射前的空中电场分析表明，引雷成功的关键除有足够长的导线以使导线两端的电场产生畸变外，另一个重要的条件是火箭－导线系统顶端能处于强的环境电场中以满足顶部流光的产生和持续传输。另外，低空较强的环境电场对火箭－导线系统下端下行流光的发展和空气间隙的击穿有重要的促进作用。一次空中引雷触发高度上的电场大于５０．０ｋＶ／ｍ，火箭－导线系统下行正流光持续传输的电场值为１９．０ｋＶ／ｍ，放电过程首先起始于火箭－导线系统下端正流光的产生。根据多年的实验资料，建议实际引雷试验时，以５００ｍ高度上的电场为参考来决定火箭的发射时刻，北方雷暴大于５０ｋＶ／ｍ，南方雷暴大于２５ｋＶ／ｍ。

INFLUENCE OF CORONA IONS NEAR THE GROUND ON THE INITIATION OF ALTITUDE TRIGGERING LIGHTNING

The electric field and charge density under one thunderstorm have been studied by using a one-dimension model. Corona ions produced from ground irregularities will reach up to 500m in 1min if they are not captured by aerosols. Space charge layer is as thick as several hundreds meters with the evolution of thunderstorm. The analyses of electric field in altitude show that there is an important factor which affect triggering lightning success besides of the length of wires spooling by the rocket. That is the rocket should reach up to higher ambient electric field for the propagation of streamer from the tip of the rocket. Meanwhile, the higher ambient electric field in lower space is conducive to the propagation of streamer at the bottom of rocket-wire system and the breakdown of the isolated gap between the bottom of wire connecting to the wire and the grounded wire. One example of electric field for successful altitude triggered lightning is about 50.0kV/m, and the discharge begins with the positive streamer initiation at the bottom of the rocket-wire system. For the artificially triggering lightning experiment, it is suggested that the rocket lunching instant could be determined by referring the electric field at 500m above the ground, which is greater than 50kV/m in northern China and 25kV/m in southern China.