Study On Lightning Plasma Conductivity

The intense current generated during the lightning discharge is the main source of various lightning disasters.The randomness of lightning makes it impossible to obtain the current parameters by direct measurement,and the transmission characteristics of the current can only be studied by indirect methods.The electrical conductivity of lightning plasma is a key factor reflecting the current carrying capacity of the discharge channel,the current is closely related to the conduction characteristics of the discharge channel,so studying the changes in the conduction characteristics of the discharge channel along the channel is of great significance to study the transmission characteristics of the current.The study of channel conductivity and spectral characteristics is helpful to explore the transmission characteristics of discharge current.At present,there are relatively few studies on the electrical conductivity in lightning discharge plasma channels.In this work,the slit-less high-speed spectrograph was used to perform the spectral observation of the natural lightning return stroke discharge process to obtain the original spectral data of 5cloud-to-ground lightning return strokes process.According to the spectral information,combined with the observation waveform of the electric field change occurring at the same time on the ground,the electrical conductivity of the lightning discharge plasma channel and the total intensity of the ionic lines in the spectra were calculated,and their variation along the channel height was further explored.The results show that the electrical conductivity of the lightning return strokes channel is about 10~4S/m,and the total intensity of the ionic lines decreases with increasing channel height,and the electrical conductivity of the channel also decreases slightly.In addition,the attenuation law of the electrical conductivity and the total intensity of the ion line with the channel height is basically the same,but there is a certain difference in the attenuation coefficient of them,and the attenuation of the conductivity along the channel height is relatively slow.The time evolution spectrum of the same lightning discharge process reflects that during the discharge process,as the current intensity gradually weakens,the total ionic lines intensity of the spectra also decreases.In most cases,the attenuation of the total ionic lines intensity along the channel gradually slows down.However,there is no obvious change in the attenuation of the electrical conductivity.The current intensity and changes of the different lightning return strokes of the same lightning are generally different,and the electrical conductivity changes are also significantly different.This characteristic shows that the factor that affects the current intensity is not just the conductivity.For the cloud-to-ground negative lightning,in the leader process before the return stroke discharge,the negative charge in the cloud moves downwards under the action of the electric field,opening up an ionization channel and storing a large amount of negative charge in the channel.The amount of charge stored in the channel during the leader phase is the main factor that determines the current intensity.It is inferred from the analysis of the calculation results that the radius of the current-carrying channel is also another factor affecting the current intensity.This work provides reference data for studying the transmission mechanism of discharge current.