A study of the Weddell Sea Anomaly observed by FORMOSAT-3/COSMIC
A study of the Weddell Sea Anomaly observed by FORMOSAT-3/COSMIC
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福尔摩沙三号/宇宙观测威德尔海异常研究
DOI：
10.1029/2009ja014175
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发表时间：
2009-12-09
影响因子：
2.8
通讯作者：
Le, Huijun
中科院分区：
文献类型：
--
作者：
He, Maosheng;Liu, Libo;Le, Huijun
为了研究威德尔海异常（Weddell Sea Anomaly， WSA）的演化，我们收集了两年多的低太阳活动时的COSMIC电子密度剖面。威德尔海异常在当地夏季表现为电子密度的夜间增强。观测结果表明，NmF2 （F2峰电子密度）的变化与hmF2 （F2峰高度）的变化密切相关，而后者与地磁场成分密切相关。结果表明：(1)下午，在jsin(2I)j值较大的地区，hmF2更容易急剧上升，在一定的赤纬下，hmF2会出现得早，南半球偏东，北半球偏西；(2)随后，hmF2的增量越大，NmF2的增强也越强，增强结束于局部日落附近；(3)在中纬度地区，分点傍晚和冬季hmF2的演变模式与夏季相似，但没有夏季那样的持续增强。这些特征表明，NmF2和hmF2的增强可能是由热层风效应引起的，而太阳光电离在增强中也起着至关重要的作用。在上述特征上，中纬度F2层在局地夏季傍晚的总体增强与WSA一致，说明WSA是风引起的傍晚增强的一种表现，具有特定的磁场几何形状。
[1] More than two years of COSMIC electron density profiles at low solar activities are collected to study the evolution of the Weddell Sea Anomaly (WSA), which appears as an evening enhancement in electron density during local summer. Observations show that the change in NmF2 (the F2 peak electron density) is associated with the change in hmF2 (the F2 peak height), while the latter is correlated closely with the components of the geomagnetic field. We find that (1) in the afternoon, hmF2 is more liable to rise drastically in regions with a larger jsin(2I)j value, which would occur early at certain declinations, eastward in the southern hemisphere and westward in the northern hemisphere; (2) subsequently, a larger increment of hmF2 is coincidentally followed by a stronger enhancement of NmF2 and the enhancement ends just around the local sunset; and (3) in midlatitudes, the evolution pattern of hmF2 in the evening of equinoxes and winter is similar to that in summer, albeit without a lasting NmF2 enhancement as that in summer. These features suggest that the NmF2 enhancement and the hmF2 increase could arise from the thermospheric wind effect, and solar photoionization plays a crucial role in the enhancement as well. The general midlatitude F2 layer enhancement in local summer evening is consistent with the WSA on the above features, indicating that the WSA is a manifestation, with a particular geometry of the magnetic field, of the evening enhancement induced by the winds.