| The time variation of the cosmic ray flux is one of crucial problems in the field of cosmic ray physics, solar geophysics and astrophysics, etc. The origin, propagation and modulation of cosmic ray can be studied through its variation. However, there is no information on the variation of 1-l0TeV cosmic ray because of the limit of the observation threshold energy and equipments.The development of EAS with ultrahigh energy reaches about its maximum at the altitude of the Yangbajing Cosmic Ray Observation Station Tibet ASy array where the density of shower particles is high, and the threshold energy is low. Therefore, it is propitious to study the variation of 1-lOTeV cosmic ray.In this thesis, wavelet transform combining with epoch folding methods is used as the data analysis method, and its validity and superiority is proved by the simulated experiments. It shows that this method is able to detect low-power level periodic signals in data with low signal-noise ratio more effectively, and give the distribution of phase. It is the first time that the method is used to search for the periodic signals of 1-l0TeV cosmic ray in the data obtained with Tibet II /HD AS Array for December of 1997 to June of 1998 and study its meteorological effect.Solar time semi-diurnal and diurnal variations have been detected with about signal-noise ratio 12.9 and 10 for the TeV and l0TeV cosmic ray flux respectively. The semi-diurnal variations are of an amplitude 0.3 ?.1 8%, a phase 0.9(llh) for TeV cosmic ray and 0.35?.23%, 0.9(llh) for lOTeV. The diurnal variations are of amplitude 0.4 ?.26%, 0.5 ?.34%, and phase 0.8(18h) for TeV and lOTeV cosmic ray respectively.Using the method above, solar time semi-diurnal and diurnal variations of meteorological parameters, including the atmospheric pressure and the temperature out of the room are analyzed. The following correlation analysis and data fit show that the obvious correlation exist between the periodic variations of trigger rate and record rate of the cosmic ray observation experiment and of the atmospheric pressure and the temperature out of theroom at the level of observation. The meteorological effect of cosmic ray is corrected by using binary regression analysis. And the correction is proved to be effective by correction inspection.The periodic analysis for the data of cosmic ray flux after meteorological effect inspection shows that solar time semi-diurnal, 0.996 and 1.002 diurnal variations exit in the data of TeV and lOTeV cosmic ray. These periodic variations have been detected with about signal-noise ratio 8.1, 5.6 and 6.4, with amplitude 0.08?.04%, 0.15 ?.087% and 0.150.095%, and phase O.l(lh), 0.7(17h) and 0.3(7h) for lOTeV cosmic ray flux respectively, and with signal-noise ratio 7.1, 5.1 and 6.1, with amplitude 0.05 + 0.031%, 0.1 0.068% and 0.125 + 0.078%, and phase 0.9(1 Ih), 0.7(17h) and 0.3(7h) for TeV cosmic ray flux respectively. The origin of these periodic variations needs more investigation.The sidereal diurnal variation of cosmic ray ties up with the most basic and important problem in cosmic ray physics such as the origin, propagation and the acceleration mechanisms of cosmic ray. The sidereal diurnal variation (T=0.997d) for lOTeV cosmic ray has been detected with about signal-noise ratio 5.0, with amplitude 0.125 + 0.079% and phase 0.45(llh) by analyzing the data of cosmic ray flux after meteorological effect corrected. The phase accords with other observation results basically, while the amplitude of variation is double. Our result of the amplitude is more close to the theory value (0.17%). The sidereal diurnal variation for TeV cosmic ray has been detected with about signal-noise ratio 4.5, with amplitude 0.10.062% and phase 0.45(1Ih).It has practical significance to process the data obtained with the famous Yangbajing Cosmic Ray Observation Station ASy array for the first time using the technique of wavelet analysis which is maturing and used largely in the signal processing combining with classical epoch folding methods, and will lay the...
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