中文摘要：

利用太阳活动高年（2000年）IGS提供的全球TEC数据，采用傅里叶展开的方法，分析了白天电离层TEC周年和半年变化的全球特征．结果显示：电离层TEC周年变化幅度在南北半球中高纬度地区较大、赤道和低纬地区很小．半年变化的幅度在“远极地区”（远离地球南北地磁极点的东北亚和南美地区）比“近极地区”（靠近地球南北地磁极点的北美和澳大利亚）大得多．进一步的统计显示，全球大部分地区TEC在春秋月份出现最大值，北半球近极地区最大值在冬季出现．南半球的南美和澳大利亚部分地区，最大值出现在夏季． 同样，采用傅里叶方法分析了中性大气模式MSIS90计算的全球大气原子分子浓度比值（[O／N2]）的数据，发现在南北半球中高纬度地区，中性成分[O／N2]周年变化幅度较大且有明显的冬季异常现象，依据Rishbeth等提出的理论，我们认为大气成分[O/N2]可能对TEC周年变化的产生有重要作用，并且也是TEC在近极地区出现冬季异常现象的主要原因．TEC半年变化的全球分布特征形成的原因较复杂，我们初步分析可能是由于中性成分[O／N2]、太阳天顶角控制的电离层光化学产生率变化共同作用而产生的．

英文摘要：

With the Fourier analysis method, the daytime ionosphere total electron concentration （TEC） are investigated by using a high solar activity years （2000） global GPS data series from IGS, the main features are outlined as follows： the annual variation of daytime TEC are strong in the middle latitudes for the northern and southern hemispheres, and weak in the low latitudes and equatorial region. The amplitudes of semiannual variation are much larger in the ＇far-pole＇ region （far away from the northern or southern magnetic pole, i.e. north-east Asia and South American） than those in the ＇near-pole＇ region （North American and Austria）. Further studies also show that daytime TEC maximize at equinox days in most regions, and maximize in winter in the northern ＇near-pole＇ region. In South America and Austria, daytime TEC reaches its max value in summer. The atomic/molecular ratio [ O/N2 ] in the neutral atmosphere calculated by the MSIS90 model are also treated with Fourier method, results indicate that the annual amplitudes of the [ O/N2 ] ratio are large in the northern and southern middle and high latitudes, and the winter anomaly are noticeable very much. According to Rishbeth＇ s opinion, we suggest that the [O/N2 ] may have important contribution to the TEC annual variation, as well as the winter anomaly in the ＇near-pole＇ region. As for the daytime TEC semiannual variations, we should comprehensively consider the contribution of [ O/N2 ] and the electron production rate associate with the solar zenith angle.