On the nature of ULF wave power during nightside auroral activations and substorms: 1. Spatial distribution
On the nature of ULF wave power during nightside auroral activations and substorms: 1. Spatial distribution
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关于夜间极光激活和亚暴期间超低频波功率的性质： 1. 空间分布
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发表时间：
2011
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通讯作者：
D. Milling
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作者：
K. Murphy;I. J. Rae;I. Mann;D. Milling
[1] 我们提出了对三个 ULF 波段（较长周期 Pi1（10-40 秒）波段、Pi1-2（24-96 秒）波段和 Pi2（40-150 秒）波段）亚暴扩展阶段爆发期间地基磁力计超低频（ULF）波功率和极化的统计分析结果，以确定这些波段在扩展阶段爆发期间是否是统计上不同的现象。利用磁层顶至极光全球探索 (IMAGE) 卫星成像仪识别的 800 多个夜间极光激活和亚暴，我们描述了相对于 IMAGE 观察到的初始极光增亮的空间和时间开始的 ULF 波功率、方位角和椭圆度的二维空间分布。我们确定了在亚暴扩展阶段开始时观测到的统计 ULF 波功率谱，并表征了三个 ULF 波段中每一个波段中 ULF 波功率的空间衰减尺度，作为纬度和经度的函数。总的来说，我们发现三个ULF波段的ULF波功率、方位角和椭圆率的空间分布与之前的案例研究一致，并且Pi1-2和Pi2波段非常相似。此外，我们发现长周期 Pi1、Pi1-2 和 Pi2 频带中 ULF 波功率的空间衰减尺度惊人地相似。最后，我们表明，统计 ULF 波功率谱具有幂律特征，没有优选频率或不连续性来区分三个 ULF 波段，这证明了研究亚暴扩展阶段爆发期间整个 ULF 谱的重要性。
[1] We present the results of a statistical analysis of ground-based magnetometer Ultra Low Frequency (ULF) wave power and polarization during substorm expansion phase onset in three ULF wave bands, the longer-period Pi1 (10–40 s) band, the Pi1-2 (24–96 s) band, and Pi2 (40–150 s) wave band, in order to determine whether these wave bands are statistically disparate phenomena during expansion phase onset. Utilizing over 800 nightside auroral activations and substorms identified by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite, we characterize the two-dimensional spatial distribution of ULF wave power, angle of azimuth, and ellipticity with respect to the spatial and temporal onset of the initial auroral brightening as observed by IMAGE. We determine the statistical ULF wave power spectra observed during substorm expansion phase onset and characterize the spatial decay scales of ULF wave power, in each of the three ULF wave bands, as a function of latitude and longitude. In general, we find that the spatial distribution of ULF wave power, angle of azimuth, and ellipticity in each of the three ULF bands is consistent with previous case studies and that the Pi1-2 and Pi2 wave bands are remarkably similar. Additionally, we find that the spatial decay scales of ULF wave power in the long-period Pi1, the Pi1-2, and the Pi2 bands are surprisingly similar. Finally we show that the statistical ULF wave power spectrum is characteristic of a power law with no preferred frequency or discontinuity to differentiate between the three ULF wave bands, demonstrating the importance of studying the entire ULF spectrum during substorm expansion phase onset.