第22与23周磁静日北京台银河宇宙线周日变化与半日变化特征

利用快速傅里叶变换及其计算功率谱的方法研究了第22和23周磁静日北京宇宙线台站记录的银河宇宙线强度的周日变化与半日变化，计算结果表明，在两个太阳活动周交替时，银河宇宙线的周日变化与半日变化特征消失，在太阳活动低年逐渐向高年过度时，首先出现的是周日变化。半日变化特征出现要滞后于周日变化，22周太阳活动高年看不出周日变化，而23周太阳活动的高年周日变化非常显著，22周太阳活动的下降期。只有周日变化而无半日变化。这是分析北京宇宙线台近2个太阳活动周数据得到的新结果。

SOLAR DIURNAL AND SEMIDIURNAL VARIATION CHARACTERISTICS OF COSMIC RAYS OBSERVED AT BEIJING NEUTRON MONITOR DURING MAGNETIC QUIET DAYS FROM SOLAR CYCLE 22 TO SOLAR CYCLE 23

Data of cosmic rays observed at Beijing Neutron Monitor Station during mag- notic quiet days from solar cycle 22 to solar cycle 23 are analysed to show the diurnal and semidurnal variation characteristics by using Fast Fourier Transformation and power spectrum estimation. The days for data analysis are so selected that not only these days be at least in a successive 6 days' period of very low magntic activi- ties, but also the previous five days with geomagntic index Ap lower than 15. The computational results show that the periodical features of diurnal and senmidiurnal of the cosmic rays disappeared during the period from one solar cycle to the next solar cycle. When solar activity gradually increased from Solar Minimum to Solar Maximum, the diurnal vartation appeared earlier than semidiurnal variation. The solar diurnal variation's magnatitude is bigger than that of semidiurnal's. Diurnal variation of cosmic rays during Solar Meximum of solar cycle 22 is not clearly seen, while on the contrary it is very distinct during solar maximum for solar cycle 23.