Multifractal analysis of geomagnetic storm and solar flare indices and their class dependence
Multifractal analysis of geomagnetic storm and solar flare indices and their class dependence
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DOI：
10.1029/2008ja013854
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发表时间：
2009-05
影响因子：
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通讯作者：
Zuguo Yu;V. Anh;R. Eastes
中科院分区：
文献类型：
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作者：
Zuguo Yu;V. Anh;R. Eastes
利用多重分形去趋势波动分析（MF-DFA）研究了1995年3月1日至2003年6月17日期间地磁活动的两个指标Dst（代表低纬）和ap（代表全球地磁活动）与太阳X射线亮度Xl的多重分形特征. MF-DFA中Dst和ap的h（q）曲线相似，但与Xl的h（q）曲线不同，表明Xl与Dst和ap的标度性质不同.因此，不应该直接从太阳X射线观测来预测磁暴的大小。然而，在每小时的测量中，太阳X射线辐照度的类别（选择的类别是为了区分X-M类、C类和B类或更少的太阳耀斑，包括没有耀斑）与活跃期间在D st和a p中看到的地磁扰动（大到中等、小或安静）之间存在很强的关系。使用三个类将每个时间序列转换为符号序列。频率，产生的措施表示，符号序列中的子串，然后表征空间天气事件的模式。利用MF-DFA方法和传统的多重分形分析，我们计算了测度表示的h（q），D（q）和τ（q）曲线.τ（q）曲线表明这三个指标的测度表示都是多重分形的。在此三类聚类的基础上，我们发现当q为正值时，这三个指标的测度表示的h（q）、D（q）和τ（q）曲线是相似的。因此，正的耀斑风暴类依赖性反映在MF-DFA的标度指数h（q）和多重分形指数D（q）和τ（q）中。这一发现表明，太阳耀斑类的使用可以提高D级的预测。
The multifractal properties of two indices of geomagnetic activity, D st (representative of low latitudes) and a p (representative of the global geomagnetic activity), with the solar X-ray brightness, X l , during the period from 1 March 1995 to 17 June 2003 are examined using multifractal detrended fluctuation analysis (MF-DFA). The h(q) curves of D st and a p in the MF-DFA are similar to each other, but they are different from that of X l , indicating that the scaling properties of X l are different from those of D st and a p . Hence, one should not predict the magnitude of magnetic storms directly from solar X-ray observations. However, a strong relationship exists between the classes of the solar X-ray irradiance (the classes being chosen to separate solar flares of class X-M, class C, and class B or less, including no flares) in hourly measurements and the geomagnetic disturbances (large to moderate, small, or quiet) seen in D st and a p during the active period. Each time series was converted into a symbolic sequence using three classes. The frequency, yielding the measure representations, of the substrings in the symbolic sequences then characterizes the pattern of space weather events. Using the MF-DFA method and traditional multifractal analysis, we calculate the h(q), D(q), and τ (q) curves of the measure representations. The τ (q) curves indicate that the measure representations of these three indices are multifractal. On the basis of this three-class clustering, we find that the h(q), D(q), and τ (q) curves of the measure representations of these three indices are similar to each other for positive values of q. Hence, a positive flare storm class dependence is reflected in the scaling exponents h(q) in the MF-DFA and the multifractal exponents D(q) and τ (q). This finding indicates that the use of the solar flare classes could improve the prediction of the D st classes.