太阳活动低年(2005—2007)期间中国低纬地区电离层foF2变化特性

Variation of foF2 layer during low solar activity period(2005-2007)in low latitude of China

利用2005—2007年广州、海口和重庆三个台站的foF2数据,研究了foF2日变化、季节变化和foF2随太阳活动的变化规律,以及空间天气事件如磁暴对foF2的影响.结果发现:foF2的日变化规律体现在日出前出现最小值,海口和广州两站在14:00—16:00出现最大值,重庆站在12:00—14:00出现最大值;春秋季foF2均值高于夏冬季节,春季高于秋季,冬季高于夏季(重庆站不明显);从2005年开始,临频值整体下降,与太阳黑子数呈现正的线性关系;在2005-08-24开始的磁暴期间在磁暴的主相发生foF2的正向扰动,在磁暴发生的第二天foF2整体呈现负向扰动.综合以上信息可知,我国低纬地区可以划分为赤道异常区和非赤道异常区,两个地区foF2有所相似但仍有不同,应结合太阳活动具体分析.

In this paper,we use the critical frequency of F 2 layer(foF2)data of three ionosonde observations at Chongqing,Guangzhou and Haikou to analyze the diurnal,seasonal and solar variations of foF2,as well as the effects of space weather events such as magnetic storms on foF2.The diurnal variation of foF2 shows a minimum before the sunrise,and in Haikou and Guangzhou the maximum occurs nearby 14:00 to 16:00 local time,while in Chongqing the maximum occurs nearby 12:00 to 14:00 local time.It is found that foF2 value is at its maximum during equinoctial months(March,April,May,September,October,November),and minimum during the summer months(June,July,August),with intermediate values during winter months(December,January,February).Besides,foF2 at spring equinox is larger than that in autumn which is not obvious in Chongqing.Overall foF2 decreases since 2005,onwards showing a positive correlation with solar activity.foF2 variations during the geomagnetic storm commencing 24 August 2005 with Dst=-184 nT are analysed.foF2 shows a positive ionospheric storm effect on the first day of the storm and negative ionospheric storm effect on the next day.In China low latitudes,it can be divided into equatorial anomaly region and normal region.In these two regions,the change rules of foF2 are similar but still different.We should make a concrete analysis of the two regions combining with solar activity.