Decay of polar cap patch
Decay of polar cap patch
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DOI：
10.1029/2010ja016297
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发表时间：
2011-05
影响因子：
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通讯作者：
K. Hosokawa;J. Moen;K. Shiokawa;Y. Otsuka
中科院分区：
文献类型：
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作者：
K. Hosokawa;J. Moen;K. Shiokawa;Y. Otsuka
[1]我们报告了一个事件，其中一个极冠补丁检测与全天空成像仪（ASI）在Resolute湾，加拿大（74.73° N，265.07° E; AACGM纬度82.9°），在夜侧。该斑块停止了与行星际磁场北转有关的反日运动，并在ASI的视场内停留了1小时以上。当斑块停滞时，它的亮度逐渐下降，这使我们能够以定量的方式研究斑块等离子体的衰减。的补丁的衰减可以定量解释的损失，通过重组的O+与环境中的N2和O2分子，如果我们假设的光学补丁的高度为295公里左右。由MSIS-E90和IRI-2007模式得到的295 km附近的斑块高度远高于235 km处的标称值，表明IRI等气候模式不适合描述斑块的实际密度分布。这可能是因为在斑块的低海拔部分，损失过程要快得多;因此，斑块的峰值海拔随着它穿过极冠而增加，因为在F区底部的快速重组。这表明，我们应该采用更高的发射高度时，我们调查光学补丁传输到夜侧极冠深处。当我们将光学数据与其他仪器（如相干雷达和全球定位系统闪烁测量）进行比较时，这些信息是很重要的，方法是在假设斑块发射高度的情况下，将全天空图像映射到地理坐标系上。
[1] We report an event in which a polar cap patch was detected with an all-sky imager (ASI) at Resolute Bay, Canada (74.73° N, 265.07° E; AACGM latitude 82.9°), on the nightside. The patch stopped its antisunward motion associated with a northward turning of interplanetary magnetic field and stayed within the field of view of the ASI for more than 1 h. When the patch stagnated, its luminosity decreased gradually, which allows us to investigate how the patch plasma decayed in a quantitative manner. The decay of the patch can be quantitatively explained by the loss through recombinations of O+ with ambient N2 and O2 molecules, if we assume the altitude of the optical patch to be around 295 km. The derived altitude of the patch around 295 km is much higher than the nominal value at 235 km obtained from the MSIS-E90 and IRI-2007 models, indicating that climatological models such as IRI are not suitable for describing the actual density profile of patches. This is probably because the loss process was much faster in the lower-altitude part of the patch; thus, the peak altitude of the patch increased as it traveled across the polar cap because of rapid recombination at the bottomside of the F region. This suggests that we should employ higher emission altitude when we investigate optical patches transported deep into the nightside polar cap. Such information is important when we compare the optical data with other instruments such as coherent radars and GPS scintillation measurements by mapping the all-sky image on the geographic coordinate system with an assumption of the patch emission altitude.