The Delayed Time Response of Geomagnetic Activity to the Solar Wind
The Delayed Time Response of Geomagnetic Activity to the Solar Wind
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DOI：
10.1002/2016ja023793
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发表时间：
2017-09
期刊：
影响因子：
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通讯作者：
R. Maggiolo;M. Hamrin;J. De Keyser;T. Pitkänen;G. Cessateur;H. Gunell;L. Maes
中科院分区：
文献类型：
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作者：
R. Maggiolo;M. Hamrin;J. De Keyser;T. Pitkänen;G. Cessateur;H. Gunell;L. Maes
我们研究了2000年至2011年一个完整的太阳周期的地磁指数和太阳风参数之间的滞后相关性。我们首先讨论这种相关性分析所需的数学假设。太阳风参数和地磁指数具有内在的时间尺度，可以平滑相关系数随时间滞后的变化。此外，与共转相互作用区和日冕物质抛射相关的太阳风结构，以及它们前面的压缩区，强烈影响滞后相关分析结果。这项工作表明，在正确解释相关性时，必须考虑到这种偏见。然后，我们的证据表明，磁层响应时间的太阳风参数涉及多个时间尺度。PC和AE指数对太阳风动压的同时快速响应（延迟约5 min）表明，太阳风对磁层的压缩可以触发亚暴活动。我们发现，PC和AE指数对行星际磁场（IMF）BZ的响应时间分别为~20和~35 min。SYM-H指数的响应时间更长（~80 min）且不太尖锐，SYM-H与IMF BZ在统计学上显著相关，直到10 h前观察到。我们的研究结果表明，太阳风速度对地磁活动的主要影响是由快/慢太阳风区域界面处的压缩区域引起的，这些压缩区域与高太阳风压和强行星际磁场有关，因此具有很强的地球效应。
We investigate the lagged correlation between a selection of geomagnetic indices and solar wind parameters for a complete solar cycle, from 2000 to 2011. We first discuss the mathematical assumptions required for such a correlation analysis. The solar wind parameters and geomagnetic indices have inherent timescales that smooth the variations of the correlation coefficients with time lag. Furthermore, the solar wind structure associated with corotating interaction regions and coronal mass ejections, and the compression regions ahead of them, strongly impacts the lagged correlation analysis results. This work shows that such bias must be taken into account in a correct interpretation of correlations. We then evidence that the magnetospheric response time to solar wind parameters involves multiple timescales. The simultaneous and quick response of the PC and AE indices to solar wind dynamic pressure with a delay of ~5 min suggests that magnetospheric compression by solar wind can trigger substorm activity. We find that the PC and AE indices respond to interplanetary magnetic field (IMF) BZ with a response time of respectively ~20 and ~35 min. The response of the SYM‐H index takes longer (~80 min) and is less sharp, SYM‐H being statistically significantly correlated to the IMF BZ observed up to more than ~10 h before. Our results suggest that the solar wind velocity's dominant impact on geomagnetic activity is caused by the compression regions at the interface of fast/slow solar wind regimes, which are very geo‐effective as they are associated with high solar wind pressure and strong interplanetary magnetic field.