Spatial distribution of average vorticity in the high-latitude ionosphere and its variation with interplanetary magnetic field direction and season
Spatial distribution of average vorticity in the high-latitude ionosphere and its variation with interplanetary magnetic field direction and season
复制标题
高纬度电离层平均涡度空间分布及其随行星际磁场方向和季节的变化
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
G. Sofko
中科院分区：
文献类型：
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作者：
G. Chisham;M. Freeman;G. Abel;W. Bristow;A. Marchaudon;J. Ruohoniemi;G. Sofko
[1]我们提出了一种利用超级双极光雷达网(SuperDARN)的视线速度测量技术来测量F区电离层中尺度等离子体流的磁场定向涡度的技术。涡度通常被用作电离层磁场对准电流强度的指标，但也提供了关于电离层和磁层中的湍流过程的信息。利用北半球6个SuperDARN雷达6年(2000-2005年包括在内)的涡度测量，我们首次编制了北极电离层平均涡度图。这些地图根据不同的季节和行星际磁场(IMF)条件进行了细分。涡度图的形态随IMF方向的变化与平均FAC强度图(用不同的方法和仪器测定)中的变化非常接近，这表明涡度在平均意义上是FAC的一个很好的替代。涡度图的形态随季节的变化与FAC图的不同，说明电离层电导在决定涡度测量值与FAC图之间的差异中起着重要作用。
[1] We present a technique to measure the magnetic field-aligned vorticity of mesoscale plasma flows in the F region ionosphere using line-of-sight velocity measurements made by the Super Dual Auroral Radar Network (SuperDARN). Vorticity is often used as a proxy for magnetic field-aligned current (FAC) intensity in the ionosphere but also provides information about turbulent processes in the ionosphere and magnetosphere. Using 6 years (2000–2005 inclusive) of vorticity measurements made by six SuperDARN radars in the Northern Hemisphere, we have compiled, for the first time, maps of average vorticity across the northern polar ionosphere. These maps have been subdivided according to different seasonal and interplanetary magnetic field (IMF) conditions. The variations in the morphology of the vorticity maps with IMF direction match very closely those seen in maps of average FAC intensity (determined using different methods and instrumentation), suggesting that vorticity is a good proxy for FAC in an averaged sense. The variations in the morphology of the vorticity maps with season show differences from those seen in the FAC maps, illustrating that ionospheric conductance plays a major role in determining the differences between measurements of vorticity and FAC.