【作者】 徐斌；

【导师】 贾焕玉；

【作者基本信息】 西南交通大学 ， 电磁场与微波技术， 2009， 博士

【摘要】 宇宙线是来自宇宙空间的高能粒子流,是人类研究宇宙的唯一物质样品。宇宙线强度随时间的变化、时间变化的起因携带有关于空间动力学过程的丰富信息,是宇宙线物理、地球物理和天体物理学科中最为复杂的问题之一,具有重要的物理意义。位于西藏羊八井镇(90.5°E,30.1°N海拔高度4300m,对应的大气深度606g/cm~2)的羊八井宇宙线观测站,于2006年6月建设完成了ARGO实验主探测器群,实验数据采集、监测和物理分析工作也随之仝面展开。宇宙线气象效应和时间变化是该实验的一项重要研究内容。本文首先介绍了有关宇宙线的基本知识及宇宙线时间变化的研究现状和存在的问题。重点讨论了ARGO-YBJ实验的硬件系统和数据采集系统,分析了该实验“Scaler模式”下4个多重数宇宙线计数。结果表明,宇宙线计数率的统计分布接近随机变量所服从的高斯分布,这说明了实验各组成部分运行正常。此外,还讨论了实验数据检测和数据筛选方法,并应用这些方法对ARGO实验“Scaler模式”数据进行了检测和筛选,得到了长时间范围内稳定可靠的实验数据,为后面的物理分析工作奠定了可靠的基础。作为大面积宇宙线探测实验,地面探测的宇宙线计数受地球气象效应的影响。对宇宙线气象效应研究一方面可以提供宇宙线大气簇射的特征信息,另一方面有助于对观测数据进行可靠的气象效应修正,从而使我们有可能发现大气影响以外的宇宙线变化。本文采用多元相关分析法研究了ARGO实验“Scaler模式”下从2005年12月到2008年6月期间的4个多重数宇宙线计数与大气压强、室内外温度和实验大厅内大气相对湿度的偏相关系数。结果表明:大气压强是影响宇宙线地面测量的主要因素,室外温度也有一定影响,实验大厅内的温度和湿度主要是通过影响探测器性能间接影响宇宙线计数,这种影响比大气压强和室外温度的影响要小很多。基于关联分析,我们对宇宙线气象效应进行了仔细修正。修正前后的关联对比分析表明,修正的结果是彻底、可靠的。利用ARGO实验气象效应修正后的数据,研究了实验室附近发生大气雷暴时次级宇宙线强度的瞬时变化。发现雷暴期间大气电场强度剧烈变化时,低多重数宇宙线计数有明显的瞬时增长,增长幅度在1%到9%之间,然后较缓慢地恢复到原来水平。这种增长事件大多发生在大气电场强度为正值时,增长的峰值出现在闪电之后。在气象效应修正的基础上,利用Lomb-Scargle Fourier变换和周期折叠法对ARGO-YBJ实验“Scaler模式”的四个多重数宇宙线计数进行短周期变化研究。结合模拟手段分析了地面测量次级宇宙线计数的太阳日和半日周期变化。结果显示4个多重数宇宙线计数都具有太阳日周期和半日周期变化,调制幅度与原初宇宙线粒子的能量(多重数)有关。原初宇宙线粒子能量越高,太阳日和半日调制幅度越小。此外,多重数为n≥4的次级宇宙线强度中还可能存在频率为1.0024的周期信号,这对应于恒星日周期(频率为1.0027)调制。半日周期变化的最小幅度处的相位约为0.45(单位0.5个太阳日);太阳日周期变化的最小幅度处的相位约为0.7个太阳日(约19时,世界时间)。最后利用ARGO实验大厅项部的大气电场仪记录的大气电场数据,研究了西藏羊八井地区近地晴天大气电场的周期变化,结果表明晴天大气电场也具有太阳日周期和半日周期变化,并且周期变化的相位与宇宙线相对计数的周期变化的相位相似,这说明晴天大气电场的周期变化可能受宇宙线强度变化的影响。更多还原

【Abstract】 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.更多还原