Cosmic Ray Yariations On The Ground During Thunderstorms

During thunderstorms, the atmospheric electric field changes violently, the strength can be up to100kV/m or more. High-energy cosmic rays from space will form extensive air shower (EAS) when they come into the atmosphere, which questions the relationship between secondary particles of EAS and thunderstorms. It has significance not only for the study of cosmic ray physics, but also for understanding the development of the climate phenomenon.ARGO-YBJ is an extensive air shower detector located at Yangbajing (Tibet, China) at4300m a.s.l.. It is made by a full coverage carpet plus a guard ring (total surface6700m2) of Resistive Plate Chambers grouped into153units called clusters. The experiment has two different operation modes, in scaler mode the apparatus records the number of events with particle multiplicity≥1,≥2,≥3,≥4over each cluster, the count rate of a cluster is40kHz,2kHz,300Hz,120Hz approximately; with the shower mode coordinates and arrival time of each particle hitting the carpet are recorded, for a complete shower reconstruction at an energy threshold of few hundreds of GeVs, the case rate of it is about3.6kHz. The high count rate of the experiment is important for careful study of the relationship between the atmospheric electric field and EAS secondary particles during thunderstorms.Thunderstorms examples were analyzed and discussed using the data of ARGO-YBJ experiment from2011to2012. There are significant changes in EAS secondary cosmic particle when there are dramatic changes in atmospheric electric field. The count rate of n=1and n=2in scaler mode increased significantly during thunderstorms and can be seen as the superposition of two different types-A type and B type. A type rises slowly and recovers slowly, duration time is long, generally two or three hours. It may be associated with the changes of radioactive substances (such as radon) in atmospheric. B type rises quickly and recovers quickly, duration time is short, generally20minutes. This may be cause by the mechanism of RREA, is an effect of atmospheric field, i.e. TGE phenomenon. The count rate of n=3and n>4is decreased during thunderstorms, which is corresponding to the increase of type B in n=1and n=2. The count rate fell of n=3is not more than1%for most example, and the count rate fell of n≥4is more significant, even be able to reach10%in some case. The count rate of n≥20in shower mode is also decreased significantly like the decrease of n>4in scaler mode. It can be found that the count rate of n=1and n=2changes slightly later than the atmospheric electric field which is about2to3minutes after we do a correlation analysis between the count rate and the atmospheric electric field. It also can be found that the count rate of n=3, n≥4and n≥20changes simultaneously with the change of the atmospheric electric field. There is a significant association between the count rate changes and the changes in the atmospheric electric field, and it can be expressed as a correlation between the count rate changes and the square of the atmospheric electric field. It is a positive correlation between the count rate of n=1, n=2and (E-p1)2, but a negative correlation between the count rate of n=3, n≥4, n≥20and (E-p1)2. It is similar with the result got by Baksan. The relationship between the count rate and the atmospheric electric field has important reference value to the study of the interaction between cosmic rays and thunderstorms.