Using a time series of geomagnetic storm events between 1957 and 2019, obtained by selecting storms where −50 nT, we have analyzed the probability of occurrence of moderate, intense, and severe events. Considering that geomagnetic storms can be modeled as stochastic processes with a log-normal probability distribution over their minimum index, the dataset was separated according to solar cycle (SC) and SC phases, and the distributions of events were fitted through maximum likelihood method in order to characterize the occurrence of storms in each cycle and phase, and then compare those occurrences to the SC24. Our results show that there is a strong dependence between the occurrence of intense storms, with  −100 nT, and the strength of the SC measured by the sunspot numbers. In particular, SC24 is very similar to SC20. However, when comparing the occurrence of storms by SC phases, events tend to show similar activity toward the minimum phase and have significant differences in the maximum phases. By looking at the value—the fit log-normal distribution “width” parameter—characteristic of the occurrence rate of storms, we have found that the (the sigma value in the descending phase of one cycle) shows the highest correlation () with (the sigma value in the maximum phase of the next cycle) which allows us to estimate the occurrence rate of storms for SC25 to be similar to those of SC21 and SC22, suggesting a more intense cycle than the one that just ended.

中文翻译：

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地磁风暴的发生及其与太阳周期阶段的关系

使用通过选择-50 nT 的风暴获得的 1957 年至 2019 年地磁暴事件的时间序列，我们分析了中度、强烈和严重事件发生的概率。考虑到地磁暴可以建模为在其最小指数上具有对数正态概率分布的随机过程，根据太阳周期（SC）和SC阶段分离数据集，并通过最大似然法拟合事件的分布，以便以表征每个周期和阶段中风暴的发生，然后将这些发生与 SC24 进行比较。我们的结果表明，强烈风暴的发生与 −100 nT，以及由太阳黑子数测量的 SC 强度。特别是，SC24 与 SC20 非常相似。然而，当按 SC 阶段比较风暴的发生时，事件往往在最小阶段表现出相似的活动，而在最大阶段有显着差异。通过观察风暴发生率的值——拟合对数正态分布“宽度”参数，我们发现（一个周期下降阶段的西格玛值）显示出最高的相关性（）与（下一个周期最大阶段的 sigma 值），这使我们能够估计 SC25 的风暴发生率与 SC21 和 SC22 相似，表明比刚刚结束的周期更强烈。