【Title】Characteristics of ELDI varying with solar activity in polar region from observations of EISCAT/ESR radars
黄定娟, 蔡红涛, 李飞, 胡坤, 李影, 余尧, 马淑英
Huang Dingjuan, Cai Hongtao, Li Fei, Hu Kun, Li Ying, Yu Yao, Ma Shuying
E-Layer Dominated Ionosphere;
incoherent scatter radar
【摘要】利用1999—2011年EISCAT(EISCAT Tromsø UHF)和ESR(EISCAT Svalbard Radar)雷达的场向电子密度观测数据, 对比分析了两处雷达观测到的极区E层占优电离层ELDI (E-Layer Dominated Ionosphere)事件在太阳活动高、低年的统计特征。地面雷达观测表明, 太阳活动水平对极区ELDI发生率的空间分布影响显著: 在太阳活动高年, ELDI在EISCAT雷达处(极光椭圆区纬度)的发生率高于ESR雷达处(极尖/极隙区纬度); 在低年则恰好相反。夏季似乎不利于ELDI的发生, 且在该季节的变化特征不受太阳活动水平及空间位置变化的影响。两部雷达在太阳活动高年观测到ELDI的季节变化规律分别与低年期间的结果相一致: 在冬季和早春, ELDI的发生率较高, 其他季节发生率较低, 夏季尤其低。在ELDI事件期间, 两处雷达观测到事件的持续时间和电离层E层厚度随太阳活动水平的变化表现出明显差异: 高年事件的持续时间总体上比低年短, 低年观测到ELDI的厚度要小于高年结果; 然而 N m E/ N m F 2 比值及 H m E却没有表现出明显依赖。
【Abstract】This study investigated the characteristics of polar E-Layer Dominated Ionosphere (ELDI) events under various solar activities, based on field-aligned measurements from the EISCAT (EISCAT Tromsø UHF) and ESR (EISCAT Svalbard Radar) instruments during 1999–2011. It was found that ELDI occurrences exhibit clear reliance on solar activity. During solar maximum, ELDI events appear more frequently at the EISCAT site (at the auroral latitude) than at the ESR site (at cusp latitude), and vice versa during solar minimum. ELDI events are rarely observed by both radars in summer, which illustrates few effects of solar activity. Seasonal variations of ELDI occurrences at both sites during solar maximum are in accordance with those during solar minimum., i.e., ELDI occurrences are higher in winter and early spring than in other seasons, especially summer. On the occurrence of ELDI events, the duration of the event and the thickness of the ionospheric E-layer show remarkable variations under different solar activity conditions: the duration is shorter and the thickness is greater during solar maximum, while N m E/ N m F 2 and H m E appear less variable.
国家自然科学基金创新研究群体项目(41521063)、国家自然科学基金项目(41374159, 41431073, 41574148)、教育部博士点基金项目(201320130141110032)资助