Variation Of The Channel Temperature In The Transmission Of Lightning Leader

According to the time-resolved spectra of the lightning stepped leader and dart leader processes,the channel temperature,its evolution characteristics with time and the variation along the channel height in the transmission process were analyzed,we also analyzed the two-dimensional speed of stepped leader.The results show that the average channel temperature of the stepped leader for analyzed lightning is about 15000 K,the leader tip has a slightly higher temperature than the trailing end,which should be caused by a large amount of electric charges on the leader tip.In addition,both channel temperature and luminosity are enhanced at the inflexion or branch point of channel in transmission,and the channel temperature gradually decreases as the stepped leader approaching the ground.The average value of two-dimensional speeds is 4.4×10⁵ m/s,and show a decreasing trend when the stepped leader conveys to the ground.For the two analyzed dart leaders,the channel temperature is about 21600 K,22000 K,respectively.the electron densities and electrical conductivity are 10¹⁷/cm³,10⁴ S/m order of magnitude,respectively.We further compared the channel temperature of stepped leader,dart leader and return stroke,it find that the dart leader has a higher channel temperature than the stepped leader but a lower temperature than the return stroke.Meanwhile,as the dart leader propagates to the ground the channel temperature obviously increases.Since the leader channel transmits downward faster than the expansion of corona channel,there is not enough time for the channel near the ground fully expand,which may be responsible for the bigger electron density in the bottom of the leader channel,so the temperature is higher.