雷暴电场对宇宙射线次级粒子μ子的影响研究

Effect of thunderstorm electric field on intensity of cosmic ray muons

西藏羊八井宇宙射线观测站的中子监测器主要探测宇宙射线次级粒子中能量在500 MeV—20 GeV的核子成分和少量的负μ子成分.本文分析了2008—2010年观测站附近发生的62次雷暴期间中子监测器和大气平均电场仪的同步观测资料,发现27次雷暴期间中子监测器计数率发生明显变化,显著性S>5σ,其中13次变化显著,显著性S>10σ.显著性S>10σ的13次个例信号变化百分比与地面电场场强幅值之间存在大体一致的变化趋势,而显著性在5σ<S<10σ之间的14次个例信号变化百分比与地面电场场强幅值之间不存在相似的变化趋势.较强雷暴当顶时中子监测器计数率变化一般不明显,而中子监测器计数率变化明显的个例则多发生于雷暴云不当顶,但探测器仍处于雷暴云下部正电荷层的控制范围之内时,或者当顶雷暴处于形成或消散阶段.Dorman等把雷暴期间中子监测器计数率的变化归因于雷暴云内电场对宇宙射线次级粒子μ子的作用,并建立了雷暴期间中子监测器计数率变化与雷暴地面电场相关联的理论.本文分析发现雷暴期间羊八井中子监测器计数率变化与地面电场场强之间相关性较小或者没有相关性,不支持Dorman的理论.

Neutron monitor（NM） in Yangbajing Cosmic Ray Observatory mainly detects nucleus components with energy in a range of 500 MeV—20 GeV and a small number of negative muons.On the basis of synchronous data of neutron monitor and atmospheric electric field during 62 thunderstorms from 2008 to 2010,obvious changes of NM counting rate during 27 thunderstorms with significance greater than S 〉 5σare found,and among them,13 cases with significance greater than S 〉 10σ.A coincident approximate change trend is found between counting rate change percentage and atmospheric electric field amplitude for 13 cases with significance S 〉 10σ.However no obvious coincident change trend is found for 14 cases with significance 5σ〈 S 〈 10σ.Obvious changes of counting rate do not occur when thunderstorm is just over electric field mill,however obvious changes occur when electric field mill is not exactly below thunderclouds but in the control of bottom positive charge layer.Dorman put forward the theory that NM counting rate changes are correlated with the atmospheric electric field,thus they attributed the former to the acceleration of the electric field to negative muons inside thunderstorms.However,there is found no evident correlation between NM counting rate charge and the atmospheric electric field in this paper,so our experiment does not support Dormanetal’s theory.