Estimating the occurrence of geomagnetic activity using the Hilbert-Huang transform and extreme value theory
Estimating the occurrence of geomagnetic activity using the Hilbert-Huang transform and extreme value theory
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使用希尔伯特-黄变换和极值理论估计地磁活动的发生
DOI：
10.1002/essoar.10502744.1
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
Elvidge S
中科院分区：
文献类型：
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作者：
Elvidge S
本文利用极值理论（EVT）在aa指数的基础上估计地磁活动的回归水平。aa指数是最长的、连续记录的地磁数据集（从1868年至今）。这个长，150年的数据集是极值分析的理想候选者。然而，由于这些数据受到大约11年的太阳周期的影响，因此它们并不像EVT所要求的那样独立和均匀分布。Hilbert - Huang变换用于识别数据中的太阳周期成分，并将数据分为太阳极大期和极小期。在这两种情况下，广义极值分布已与数据集拟合。这些数据也被合并起来估算总体返回时间。结果表明，数据库中最大的事件（1989年3月）是25年1年的事件。然而，单独考虑太阳极大期和极小期对返回时间有很大的影响。在太阳极小期条件下，1989年3月事件的返回时间为130年。这表明极端空间天气事件的发生有条件地取决于我们在太阳周期中的位置。
In this paper extreme value theory (EVT) has been used to estimate the return levels for geomagnetic activity based on the aa index. The aa index is the longest, continuously recorded, geomagnetic data set (from 1868 to present). This long, 150‐year data set is an ideal candidate for extreme value analysis. However, the data are not independent and identically distributed as required for EVT since they are impacted by the approximately 11‐year solar cycle. The Hilbert‐Huang transform has been used to identify the solar cycle component in the data, and the data have been split into solar maximum and minimum times. In these two regimes the generalized extreme value distribution has been fit to the data sets. These have also been combined for an estimate of the overall return times. The results suggest that the largest event in the database (March 1989) is a 1‐in‐25‐year event. However, considering separate solar maximum and minimum times has a large impact on the return times. During solar minimum conditions the return time of the March 1989 event is 130 years. This suggests that the occurrence of extreme space weather events is conditionally dependent on where in the solar cycle we are.