The Cosmic Rays Solar Diurnal Anisotropy Observed With Neutron Monitor

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 CRs 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. With the study of the CRs’ solar diurnal anisotropy we can get the important informations about CRs’ produce and transmission areas.It’s important issues of cosmic rays’ studies.This paper introduced the basic theory of cosmic ray physics in details, including the discovery of CRs and the development process, the composition and energy spectrum of CRs, and the brief history of cosmic rays variation etc. Secondly, introduced the cosmic ray observatory, how the neutron monitors work, and the mode of data recording.. Then made a detailed exposition the analysis method for this study,including:air pressure correct、Lomb-Scagle Fourier transform analysis and Statistical folding cycle analysis. We combine the observation data of different stations,includ:Yangbajing neutron observation statio、Potchefstroom neutron observation station and Tsumeb neutron observation station to analysis CRs’daily successive variation,respectively.Before used the datas of Yangbajing neutron monitor to analyze CRs’ daily successive variation,we should corrected their pressure effect firstly.The dates of Potchefstroom neutron observation station and Tsumeb neutron observation station Can be analyzed the variation for directly,because they were corrected.We analyze the temporal variation of the solar diurnal anisotropy of cosmic rays rate observed with the Yangbajing neutron monitor during1999-2011.We find 0.5day and lday period signals,and their corresponding false alarm probability are less than 10-10For calculated the monthly mean count rates varying with time of 0.5day and lday period signals, we find a temporal variation for 11 years. Through the analysis of percentage change,we find that with the same station,the greater the count rate, the smaller the percentage change of 1 day period signals. Combine with the percentage change and their respective geographical position,we find:the percentage change of 0.5 day period signals increases with the decrease of the cut-off rigidity; And the percentage change of 1 day period signals decreases with the decrease of the.We have checked the time dependence of the phase and the amplitude of semidiurnal and diurnal anisotropy, and find that the phase of 1day signal has a observably yearly variation; the amplitude before 2010 is obvious smaller than that after 2010. These results are of great reference value for studying the anisotropy and time variation of cosmic rays.