The Effect Of Electrification On The Triggering Of Streamers By Water Particles

How lightning is triggered in a thunderstorm cloud is still a mystery.The key question is how lightning is triggered in a background electric field that is an order of magnitude lower than the breakdown threshold.In this paper,several important parameters affecting streamer triggering of hydrometeors are investigated,and streamer triggering from isolated hydrometeors in a uniform electric field is simulated.In the process of simulation,three key parameters of hydrometeor size,shape and surface electric quantity on hydrometeor were considered.In addition,the effect of the initial electron density of the environment on the streamer trigger is also studied.If the hydrometeors are not charged,the simulation results show that larger hydrometeors are more likely to trigger streamer discharges at lower ambient electric fields.For charged hydrometeors,the Coulomb electric field generated by the amount of charge on the surface of the hydrometeors enhances the local electric field of small size hydrometeors significantly.The electric charge can significantly reduce the ambient electric field needed to induce streamers from small hydrometeors.The electric field measured in a thunderstorm cloud is one order of magnitude lower than the air breakdown electric field,usually around 0.1₆)in a thunderstorm cloud and does not exceed 0.3₆).In this paper,a spherical hydrometeor with a radius of 0.5mm and a charge of 180p C is used to simulate the streamer discharge,and the results show that the streamer discharge can be triggered successfully in an ambient electric field of 0.1₆).This value is within the range of the thunderstorm cloud field,and the simulation results can explain the triggering of lightning in the thunderstorm cloud.By comparing the simulation results of spherical and rod-shaped hydrometeors with no charge,it can be found that the rod-shaped hydrometeors are more likely to cause streamers for the same radius hydrometeors.When the hydrometeors are charged,the smaller spherical hydrometeors are more likely to cause streamer discharge than the rod-shaped hydrometeors of the same size.When the size of the hydrometeor is large,the charge has little effect on the minimum electric field of streamer initiation from the spherical and rod-shaped hydrometeor.According to the simulation results,the electric field generated by the amount of charge carried by the hydrometeor plays a dominant role when the size of the hydrometeor is small,while the shape of the hydrometeor has a greater effect when the size of the hydrometeor is large.Meek number can be used to judge whether the streamer trigger can be realized.In addition,the simulation of streamer with different electron densities in the environment shows that the electron densities in the environment do not affect the triggering and evolution of streamer,but only affect the time of streamer formation.