依据不同波段光谱诊断闪电回击通道温度

Diagnosis of lightning return stroke channel temperature according to different band spectra

利用高速无狭缝光栅摄谱仪捕获到的一次闪电光谱资料,结合等离子体光谱理论,选用不同波段的光谱信息估算了闪电回击通道温度.结果表明:用不同波段的谱线组—单电离氮原子(NII)、中性氧原子(OI)和中性氮原子(NI),基于玻尔兹曼图法估算的闪电回击通道平均温度分别为43270 K,17660 K和17730 K;同时用NII和NI两个谱线组,基于萨哈-玻尔兹曼图法估算得到的闪电回击通道平均温度为24770 K.依据闪电通道电晕鞘模型和光谱辐射理论推断,单独选用NII谱线组获得的温度应该是闪电回击通道核心的温度,单独选用NI或OI谱线组获得的温度应该是围绕在闪电回击通道核心周围电晕鞘的温度;同时选用NII和NI谱线组,获得的温度应该是在曝光时间内整个通道截面(包括通道核心和电晕鞘)的平均温度.

The spectral data of a lightning discharge process are captured by a high-speed slit-less grating spectrograph.Based on the plasma spectrum theory,the lightning return stroke channel temperature is estimated according to the spectral information of the different bands.The results show that the average temperatures of the lightning return stroke channel estimated by the Boltzmann plot method are 43270,17660and 17730 K,respectively,when the spectral line group of the single ionized nitrogen atom(NII),neutral oxygen atom(OI) and neutral nitrogen atom(NI) are selected respectively.The average temperature of the lightning return stroke channel is 24770 K,which is estimated based on the Saha-Boltzmann plot method by using NII and NI spectral line groups.Based on the lightning channel corona sheath model and the spectral radiation theory,it can be inferred that the temperature obtained by using only NII spectral line group should be the temperature of the lightning return stroke channel core,and the temperature obtained by using only NI or OI spectral line group should be the temperature of the corona sheath around the lightning return stroke channel core.Using both NII and NI spectral line groups,the obtained temperature should be the average temperature of the entire channel section(including the channel core and corona sheath) in the exposure time.