南极中山站冬季电离层的平均特性

本文利用南极中山站的数字式电离层垂直测高仪１９９５年的频高图资料，对中山站上空冬季电离层的一些平均特性进行了初步分析。中山站冬季电离层Ｆ层很不稳定，其日变化比较明显，ｆｏＦ２的月中值在０９００ＵＴ出现极大并在１４００ＵＴ附近出现次极大。最大值在０９００ＵＴ（磁中午）附近，这是极隙区软电子沉降、极区等离子体对流和光辐射电离效应等诸多因素综合作用的结果，形成了所谓的磁中午异常。在２０００～０１００ＵＴ之间ｆｏＦ２数值较小，可能是由于这段时间中山站正处于电离层极洞区域。Ｅｓ层几乎每天都可以观测到，在１７００ＵＴ附近出现机率较高，并且ｆｏＥｓ数值较大，多数为极光型Ｅｓ，主要是由于极光粒子沉降引起的。电离层Ｅ层的变化相对平缓。

MEAN IONOSPHERIC PROPERTIES IN WINTER AT ZHONGSHAN STATION,ANTARCTICA

Ionograms taken from a Digisonde Portable Sounder (DPS 4) at Zhongshan Station of Antarctica in 1995 are used to analyse the mean ionospheric properties in winter.The F region is rather unstable in winter and has large diurnal variation.The monthly medium value of foF2 has a peak around 0900UT when maximum value occurs and a sub peak between 1300-1500UT.It may be effected synthetically by the low energy electron precipitation in cusp region,the high latitude plasma convection and the solar radiation,resulted in so called F region magnetic noon phenomena.Low values of foF2 occur in post midnight (2000-0100UT) when Zhongshan Station crosses the ionospheric polar hole.Sporadic E layer which caused mostly by auroral particle precipitation can be observed almost every day with the highest value of foEs around 1700UT.The diurnal variation of E layer is relatively smooth.