赤道异常的行星波周期振荡的统计特征与逐年变化及其QBO调制

利用赤道异常峰区台站(Okinawa)观测的,f_0F_2资料(1977—1990),分析计算了赤道电离层行星波周期振荡(2日、3—4日、5—7日及10—16日)的特征及其变化规律,发现其在一年四季都有出现,但相对强度在冬、夏季较大,且冬季更强;其振荡周期也随季节有所变化,以2日波而言,夏季更接近于2日,而冬季则多在2日多至2日半区间振荡;更长周期的波的所谓夏季峰值的出现,还有向夏初和夏末过渡的趋势。并发现振荡与太阳活动性呈负相关,即低年的相对幅度要强于高年,并且周期越长负相关越显著;同时显示出振荡的出现率及频率变化受到QBO的调制,QBO东风相期间比西风相更易于出现长周期振荡。这些结果说明赤道电离层明显受到中低层大气动力学变化的向上耦合的影响。

CHARACTERS OF PLANETARY SCALE OSCILLATIONS IN THE EIA AND ITS YEARLY VARIATION AND RESPONSE TO THE QBO

Long period oscillations of plasma in the equatorial ionization anomaly (EIA) are analyzed with the data from the EIA crest-region station (Okinawa) during 1977-1990. The oscillations have periods at 2-2.5, 3-4, 5-7 and 10-18 days, and make an appearance in all seasons. Its relative amplitude, however, are large in summer and even larger in winter months. There is also slight variation on seasonal distribution for different periods. The 2 day wave is stronger in summer and the near 2.5 day wave in winter. The summer amplitude peak of the longer period oscillations tends to split and shift to the beginning and end of the summer month. All these characters are consistent with the observational results of the neutral wind oscillations in the mesosphere. In the year-by-year variations, it is revealed that the EIA long-period oscillations are negatively correlated with the solar activity, and the longer the period the more obvious the negative correlation. We also show that the occurrence of the 2-2.5 day wave and period at 10-16 day wave are modulated by the equatorial QBO. In east phase of QBO, it is easier to see the EIA long period oscillations.