Night-time sudden commencements observed by CHAMP and ground-based magnetometers and their relationship to solar wind parameters
Night-time sudden commencements observed by CHAMP and ground-based magnetometers and their relationship to solar wind parameters
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DOI：
10.5194/angeo-27-1897-2009
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发表时间：
2009-05
影响因子：
1.9
通讯作者：
H. Lühr;K. Schlegel;T. Araki;M. Rother;M. Förster
中科院分区：
文献类型：
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作者：
H. Lühr;K. Schlegel;T. Araki;M. Rother;M. Förster
抽象的。我们研究了41突然开始（SC）使用同步磁场数据从CHAMP卫星和地面站的年份2000-2007。它们都是夜间事件，因为电离层电流对SC的影响应该在夜间最小。我们对地磁纬度低于±40°的研究证实了这一点。我们进一步发现，SC签名在卫星高度和地面上的起始时间是相同的，在10秒的不确定性和相应的磁场变化的斜率是非常相似的。对于磁纬向极±40°，卫星和地面上的SC幅度都增加，可能是场向电流的结果。CHAMP有时会记录到与地面不同的小尺度磁场变化，这可以用局部电离层电流来解释。利用ACE资料，我们还研究了CHAMP观测到的SC振幅与相应的太阳风动压突变之间的关系。我们的研究结果与早期的研究使用地面数据和理论预期。事实证明，在低纬度地区，地球上的感应效应相当小。另一个重要的结果是，地球附近的磁签名是过成比例地减少弱SC事件。准确性和我们的结果的不确定性的讨论完成的文件。
Abstract. We have studied 41 Sudden Commencements (SC) using simultaneous magnetic field data from the CHAMP satellite and ground stations of the years 2000–2007. They are all night time events, since the influence of ionospheric currents on the SC is supposed to be minimal at night. This is confirmed by our study for geomagnetic latitudes below ±40°. We further found that the onset times of the SC signature at satellite altitude and on the ground are the same within an uncertainty of 10 s and that the slopes of the corresponding magnetic field variation are very similar. For magnetic latitudes poleward of ±40° the amplitude of SCs increases both at the satellite and on ground, probably a consequence of field-aligned currents. CHAMP sometimes records small-scale magnetic variations different from the ground, which can be explained by local ionospheric currents. We also studied the relationship between the SC amplitude seen by CHAMP and the corresponding abrupt solar wind dynamic pressure change, using ACE data. Our results are compared with earlier studies using ground-based data and with theoretical expectations. It turns out that the induction effect in the Earth is quite small at low latitudes. Another important result is that the magnetic signature near the Earth is over-proportionally reduced for weak SC events. A discussion of accuracy and the uncertainty of our results completes the paper.