太阳活动高年海南地区电离层Es临界频率特性研究

The Study of the Critical Frequency of Ionosheric Sporadic E Layer Observed at Hainan Station During the Solar High Active Year

利用海南站数字测高仪在2002年太阳活动高年观测到的偶发E层(Es)临界频率(foEs)数据,统计分析了Es层foEs的逐日分布、日中值日变化和日发生率分布特性。结果表明(1)绝大部分临界频率foEs值小于10 MHz,foEs大于10 MHz的情况仅在夏季出现较多;(2)foEs日中值从7点左右开始迅速升高,在10点左右达到极大值,并一直维持到14点左右,之后缓慢下降;(3)Es层发生率在夏季最高,其次是秋冬季,最低为春季。分析表明,风剪切理论能够较好地解释Es日中值日变化,但却不能充分解释Es发生率及foEs大于10 MHz的分布特性。还需考虑太阳辐射水平等因素对foEs分布的影响。这些结果对于低纬电离层Es不规则体的变化规律研究具有重要的科学意义。

The critical frequency（foEs） parameters of ionospheric Sporadic E（Es） layer observed by digisonde at Hainan station in the solar high active year are utilized to analyze the features of the day-to-day distributions,medium value diurnal variations of foEs and occurrence rate of Es.The results show：（1） Most of foEs values are less than 10 MHz,and the distribution of foEs 10 MHz is concentrated in summer;（2） The medium values of foEs rose rapidly at about 07∶00,then reached the maximum at about 1 000 and maintained it until 1 400,after then descended slowly;（3） The occurrence rate of Es is the highest in summer,then in autumn and winter,the lowest in spring.The vertical wind shear theory can interpret well the medium value diurnal variations of foEs,however,it should be not enough to explain on distribution of foEs 10 MHz and occurrence rate of Es.The factors such as solar radiation level are considered further to affect the foEs.These results are very significant to the study of the ionospheric Es irregularities,especially in the low latitude.