太阳活动高、低年东亚中、低纬地区扩展F特性比较研究

扩展F(Spread-F)作为重要的电离层不规则结构之一,对电波传播、导航、通讯等有重要的影响,因此对其时、空特性的研究一直倍受重视.本文通过分析低纬海南台站和中纬长春与乌鲁木齐台站的测高仪数据,比较研究了太阳活动高、低年我国中、低纬地区夜间电离层扩展F的发生特性.扩展F发生率特性主要体现在:无论低纬还是中纬太阳活动低年扩展F发生率最大值高于太阳活动高年;无论太阳活动高年还是低年低纬站扩展F发生率最大值高于中纬站.细节特征主要体现在:首先,三台站在太阳活动高、低年扩展F发生率都存在双峰结构.太阳活动高年,低纬海南站双峰结构集中在春、秋分季节,而中纬站则集中在冬、夏季节,扩展F较容易发生的地方时低纬站主要集中在子夜前,而中纬站则偏向子夜后;在太阳活动低年,中、低纬双峰结构都出现在冬、夏季节,低纬海南站扩展F较突出的出现在子夜前后,而中纬台站则主要出现在子夜及子夜后.其次,双峰结构中的细节表现不同,如低纬海南站太阳活动高年扩展F较容易发生在春分季节,但2月和4月份发生率都比较高而且接近,而太阳活动低年扩展F较容易发生在夏季月份,但5月和7月的发生率也都比较高且接近,且太阳活动高、低年低纬主峰峰值非常接近,不像中纬地区有明显的差异等.本文针对实测数据进行了详细的分析并结合已有研究进行了细致的讨论.

Comparative study on characteristics of spread-F at low-and mid-latitudes during high and low solar activities over East Asia

In this work, we analyze the ionosonde data sets from the low-latitude station, Hainan, and mid-latitude stations, Changchun and Ürümqi. Then we conduct comparison of low-and mid-latitude spread-F occurrence rates during high and low solar activities. The results of spread-F occurrence rates include two aspects:(1) The maximum spread-F occurrence rates over both low-and mid-latitudes during low solar activity are larger than those during high solar activity. (2) During both high and low solar activities, the maximum occurrence rate over low-latitudes is greater than that over mid-latitudes. In addition, there are also some detailed characteristics of spread-F occurrence. (1) Double-peak structure exists in spread-F occurrence during high and low solar activities over all three stations. During the equinox months of the high solar activity, the two occurrence peaks over the low-latitude station occur in pre-midnight, whereas those during the solstices over mid-latitude stations of Changchun and Ürümqi occur in the post-midnight period. During low solar activity, the two peaks appear in the solstices over both low-and mid-latitude stations. Over Hainan, the main peak during summer occurs around midnight and the sub-peak during winter occurs at post-midnight. Over Changchun and Ürümqi, the two peaks occur at post-midnight. (2) Differences also exist in the detailed double-peak structure. First, the main peak over low-latitude occurs in vernal equinoctial months during high solar activity, but the maximum occurrence rates in February and April are relatively high and closer; the spread-F tends to occur in summer during low solar activity over Hainan, but the maximum occurrence rates in May and July are also relatively high and closer. During high and low solar activities, the main peak values over low-latitudes are very close, but have notable differences over mid-latitudes. In sum, a detailed analysis and comparison on characteristics of spread-F over the low-latitude station, Hainan and mid-latitude stations, Changchun and Ürümqi, are presented in this paper.