Presunrise ion temperature enhancement observed at 600 km low‐ and mid‐latitude ionosphere
Presunrise ion temperature enhancement observed at 600 km low‐ and mid‐latitude ionosphere
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DOI：
10.1029/2002gl016268
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发表时间：
2003-02
影响因子：
5.2
通讯作者：
C. Chao;S. Su;H. Yeh
中科院分区：
文献类型：
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作者：
C. Chao;S. Su;H. Yeh
本文利用中华卫星-1/IPEI观测资料，研究了2000年太阳活动极大年平静期低纬和中纬电离层顶面离子温度的地方时、经、纬和季节变化。统计结果表明，在日出前扇区有两个显著的观测值。也就是说，无论是夏季还是冬季，600 km低纬和中纬电离层日出前最早的离子温度增加总是从冬季半球开始;夏季6月期间，最强的日出前离子加热区域位于165°和195°之间的纵向区域，冬季12月期间位于285°和345°之间。我们的简单计算表明，卫星高度上的温度升高是由磁共轭点（日出时间较早）产生的光电子加热过程造成的。然而，在最强的日出前离子加热区域增强光电子加热的机制仍然不清楚，因为观测到的离子密度和场流数据未能为当前观测提出的加热机制提供明确的支持。
The quiet‐time low‐ and mid‐latitude topside ionospheric ion temperature measured with ROCSAT‐1/IPEI instrument is studied for local time, longitudinal, latitudinal, and seasonal variations for the solar maximum year of 2000. The statistical result shows two significant observations at the presunrise sector. Namely, the earliest presunrise ion temperature increase at 600 km low‐ and mid‐latitude ionosphere always starts in the winter hemisphere for both summer and winter seasons; and the strongest presunrise ion‐heating region is located in the longitudinal region between 165° and 195° during June summer and between 285° and 345° during December winter. Our simple calculation indicates that the temperature increase at the satellite altitude results from the heating process of photoelectrons that are produced at the magnetic conjugate‐point where sunrise is at an earlier time. However, the mechanism to enhance the photoelectron heating at the strongest presunrise ion‐heating region is still not clear, because the observed ion density and the field flow data fail to lend a clear support to the proposed heating mechanism for the current observations.