Observations of discrete, global magnetospheric oscillations directly driven by solar wind density variations
Observations of discrete, global magnetospheric oscillations directly driven by solar wind density variations
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DOI：
10.1029/2002ja009676
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发表时间：
2003-06
影响因子：
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通讯作者：
L. Kepko;H. Spence
中科院分区：
文献类型：
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作者：
L. Kepko;H. Spence
在本文中，我们提出了六个事件，其中太阳风数密度波动和磁层磁场观测的时间序列和频谱内容在几小时到12小时的间隔内高度相关。波动是周期性的，发生在离散频率上，通常与f = 1.3, 1.9, 2.6和3.4 mHz振荡相匹配，这些振荡归因于全球磁层MHD腔和/或波导模式。在频率低至f = 0.1 mHz的sub-mHz区域，我们也观察到显著的功率。我们表明，这些波动首先是在远离地球上游的太阳风中观察到的，并认为对流密度扰动缓慢地改变了磁层空腔的大小，导致了多次离散磁层振荡的出现。我们认为，对于这些事件，离散频率是太阳风的固有特性，与磁层可能的腔或波导模式无关。然后，我们表明，当转换为长度尺度时，密度波动组织成L = 23, 30, 45和80-100 RE的尺度。最后，我们推测了周期太阳风结构的可能太阳源。
[1] In this paper we present six events in which both the time series and the spectral content of solar wind number density fluctuations and magnetospheric magnetic field observations were highly correlated for intervals ranging from a few to twelve hours. The fluctuations were periodic and occurred at discrete frequencies which often matched the f = 1.3, 1.9, 2.6, and 3.4 mHz oscillations that have been attributed to global magnetospheric MHD cavity and/or waveguide modes. We also observed significant power in the sub-mHz region, with frequencies as low as f = 0.1 mHz. We show that these fluctuations were first observed in the solar wind, far upstream from the Earth, and argue that the convected density perturbations slowly alter the size of the magnetospheric cavity leading to the appearance of multiple, discrete magnetospheric oscillations. We argue that for these events the discrete frequencies were an inherent property of the solar wind and were not related to a possible cavity or waveguide mode of the magnetosphere. We then show that the density fluctuations, when converted into length scales, organize into scale sizes of L = 23, 30, 45, and 80–100 RE. Finally, we speculate on a possible solar source for the periodic solar wind structures.