东亚扇区中低纬地区电离层暴的统计分析

用1957~2006年间515个主相单步发展的磁暴事件，分析东亚扇区4个中低纬台站的电离层扰动类型及电离层暴开始时间，得到该地区电离层暴随纬度、季节和地方时的分布规律.研究表明，中纬区负暴明显，低纬区正暴明显；夏季负暴比正暴多，冬季正暴比负暴多，春秋季正负暴分布表现出明显的纬度差异.在东亚扇区，中纬区负暴开始时间主要分布在夜间及清晨时段，且在正午至午后时段极少发生.低纬区正暴开始时间主要发生在白天时段，且在夜间18~21 LT时段也易发生正暴.中低纬电离层正相暴平均延迟时间在10 h以内，负相暴平均延迟时间在10 h以上，且中纬区延迟时间明显比低纬区短.电离层暴延迟时间与磁暴主相开始时间对应的地方时很相关，正相暴对白天发生的磁暴比对晚上发生的磁暴响应快些，而负相暴正好相反.但电离层暴延迟时间与磁暴强度之间并没有十分明显的依赖关系.

Statistical study of the storm effects in middle and low latitude ionosphere in the East-Asian sector

On the basis of the foF2 observed from four ionosonde stations in the East-Asian sector during 515 magnetic storms from 1957 to 2006,we statistically analysis the types,the onset times and the time delay of ionospheric storms to reveal the distributions of the ionospheric response during storms related to geomagnetic latitude,season and local time.The result shows that,the negative responses prevail at mid latitude,whereas the positive responses prevail at low latitude.There are more negative storms in summer and more positive storms in winter.In equinox,the distribution of ionospheric storms shows latitudinal difference.At mid latitude,most negative phase onsets are within the night to early morning sector,and they are rarely occurred in the noon and afternoon sectors.At low latitude,positive phase onsets commence most frequently in the local daytime sector,also they commence a lot at 18~21 LT.The average time delay for ionospheric positive storms is mostly within 10 hours,while it is longer than 10 hours for negative storms,and the time delay is significantly shorter for mid latitude than for low latitude.The time delay has large dependence on the local time of MPO.The time delay of positive response is low for daytime MPO and high for nighttime MPO,whereas the opposite applies for negative response.But there is no significant relationship between the time delay and the intensity of magnetic storms.