Study Of The Meteorological Effect And Time Variation Of Cosmic Ray With ARGO-YBJ Experiment

Cosmic rays(CRs) are the high energy particles coming from astrospace,which is the only sample for human to study the universe.The time variation of CR and its origin carring the abundant information about the process of space dynamics,are one of the most complex problems in cosmic ray physics,astrophysics and geophysics,and have great significance physics meaning.The YBJ High Altitude Cosmic Ray Laboratory is located at Yangbajing town in Tibet(90°31′50″E,30°06′38″N,4300 m a.s.l.,606 g/cm~2).The installation of the central part of the detector clusters was finished in Jun,2006.At the same time,the work about the Acquisition,Detection,and Analysis of experiment Data was carried out.The study of the Meteorological effect and time variation are the important contents.In this paper,the author briefly introduces the basic knowledge of cosmic rays,the status of time variation and the existing problem of the cosmic ray study in chapter 1 and 2.In chapter 3,the hardware system and the data Acquisition system are discussed emphatically.The 4 multiplicities counts of "Scaler mode" are analyzed in chapter 4. The result shows that the statistical distribution of cosmic ray counts is similar to the gauss distribution followed by random variable.These conclusions imply that every part of the experiment is working stably.Then,we introduce the data detection and selection method,and selecte the "Scaler mode" counts with these methods.These works ensure the stability of the data which will be used for later analyses.As the experiment of cosmic ray detecting,the cosmic ray detected on the ground counts could be affected by the Meteorological effects.In the one hand,the study of the Meteorological effect could offer the characteristic information about EAS;on the other hand,it could help to correct the Meteorological effect from the data detected on the ground,and search the other physics variation besides meteorological effect.In this paper,the correlation between the 4 multiplicity cosmic ray counts(form Dec 2005 to Jun 2008) and some environmental variables(such as the atmospheric air pressure, temperature outside and inside,and humidity) is discussed by using multivariate correlation method.The result shows that atmosphere air pressure is the main factor influencing the detection of cosmic ray on the ground.The outside temperature is also an important factor.Besides,inside temperature and the humidity affect indirectly the counts by changing the performance of detector,but this effect is less important than atmosphere air pressure and outside temperature.On the bases of analysis of correlation, the 4 multiplicity cosmic ray counts are corrected by multi meteorological parameters. The result shows that this correction is thorough and dependable.The instantaneous variation of cosmic ray counts during thunderstorms when the Atmospheric Electric Field(AEF) has violent changes near the experiment hall is studied with the corrected "Scaler mode" counts of ARGO-YBJ experiment.The result shows that low multiplicity cosmic ray counts has obvious instantaneous increase(1%to 9%) when AEF has violent changes,and return to the original level slowly.The increases of secondary cosmic rays are observed predominantly in association with negative AEF but sometimes also with positive fields and the enhancements occurred before and also after lightning strokes.Based on meteorological effect correction,the short periodic variation of 4 multiplicity cosmic ray counts of "Scaler mode" are studied by using Lomb-Scargle Fourier transformation and period method.Then,the author analyzes the solar diurnal and semi-solar diurnal periodic variation of the secondary cosmic ray intensity detected on the ground,combining with simulation method.The results show that the secondary cosmic rays intensity has solar diurnal and semi-solar diurnal modulations at level 0.1%; the amplitude is lower with the energy increasing.Besides,the secondary cosmic ray intensity of n≥4 has periodic modulations with the frequency 1.0024,which corresponds to the frequency of sidereal periodic variation.The phase of least amplitude of semi-solar diumal periodic variation is about 0.45(the unit is semi-solar day).The phase of least amplitude of solar diurnal periodic variation is about 0.7solar day.At last,the solar diurnal periodic variation of the Fair-weather atmospheric electric field near the ground is analyzed.The result of its phase distribution is similar to the result of the secondary cosmic ray intensity.So this conclusion explains that the variation of atmospheric electric field may be affected by the variation of cosmic ray intensity.