The Impact of Sudden Commencements on Ground Magnetic Field Variability: Immediate and Delayed Consequences
The Impact of Sudden Commencements on Ground Magnetic Field Variability: Immediate and Delayed Consequences
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DOI：
10.1029/2021sw002764
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发表时间：
2021-06
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影响因子：
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通讯作者：
Andrew W. Smith;C. Forsyth;J. Rae;C. Rodger;M. Freeman
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作者：
Andrew W. Smith;C. Forsyth;J. Rae;C. Rodger;M. Freeman
我们研究了突然开始（SCs）和风暴突然开始（ssc）如何影响作为地磁纬度函数的磁场(R)高变化率的发生。这些快速、高振幅的地磁场变化对地面基础设施（如电网）构成重大风险，因为它们是地磁感应电流的驱动因素。我们发现近赤道站的~ 30 nT min - 1的变化率在SC中的可能性是任何随机间隔的700倍。这个因素随着地磁纬度的变化而减小，因此在30 nT min - 1左右的变化率在65°时的可能性只增加10倍。在赤道纬度，我们发现超过50 nT min - 1的所有R中有25%发生在南海。这一比例也随地磁纬度的变化而减小，下降55°时达到≤1%。然而，从SC到之后3天的时间周期占50 nT min - 1以上的地磁场波动的≥90%，直至~ 60°纬度。在60°以上，其他现象，如孤立的亚暴占了大r的大部分。此外，在南海期间和之后观测到的高变化率完全是由那些被归类为南海的现象引起的。这些结果表明，在中低纬度地区，SSCs是大R的主要风险事件，但SC本身的风险随纬度而降低。
We examine how Sudden Commencements (SCs) and Storm Sudden Commencements (SSCs) influence the occurrence of high rates of change of the magnetic field (R) as a function of geomagnetic latitude. These rapid, high amplitude variations in the ground‐level geomagnetic field pose a significant risk to ground infrastructure, such as power networks, as the drivers of geomagnetically induced currents. We find that rates of change of ∼30 nT min−1 at near‐equatorial stations are up to 700 times more likely in an SC than in any random interval. This factor decreases with geomagnetic latitude such that rates of change around 30 nT min−1 are only up to 10 times more likely by 65°. At equatorial latitudes we find that 25% of all R in excess of 50 nT min−1 occurs during SCs. This percentage also decreases with geomagnetic latitude, reaching ≤1% by 55°. However, the time period from the SC to 3 days afterward accounts for ≥90% of geomagnetic field fluctuations over 50 nT min−1, up to ∼60° latitude. Above 60°, other phenomena such as isolated substorms account for the majority of large R. Furthermore, the elevated rates of change observed during and after SCs are solely due to those classified as SSCs. These results show that SSCs are the predominant risk events for large R at mid and low latitudes, but that the risk from the SC itself decreases with latitude.