A superposed epoch analysis is conducted for five geomagnetic storms in the years 2005 and 2006 with the aim to understand energetic particle flux variations as a function of L-shell, energy and time from the Dst minimum. Data measured by the low-altitude DEMETER spacecraft were used for this purpose. The storms were identified by a Dst index below −100 nT, as well as their being isolated events in a seven-day time window. It is shown that they can be categorized into two types. The first type shows significant variations in the energetic particle fluxes around the Dst minimum and increased fluxes at high energies (>1.5 MeV), while the second type only shows increased fluxes around the Dst minimum without the increased fluxes at high energies. The first type of storm is related to more drastic but shorter-lasting changes in the solar wind parameters than the second type. One storm does not fit either category, exhibiting features from both storm types. Additionally, we investigate whether the impenetrable barrier for ultra-relativistic electrons also holds in extreme geomagnetic conditions. For the highest analyzed energies, the obtained barrier L-shells do not go below 2.6, consistent with previous findings.

中文翻译：

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低空DEMETER航天器观测到的重要地磁风暴周围高能粒子通量的变化

对 2005 年和 2006 年的五个地磁暴进行了叠加历元分析，目的是从 Dst 最小值了解作为 L 壳、能量和时间函数的高能粒子通量变化。为此，使用了低空 DEMETER 航天器测量的数据。风暴由低于 -100 nT 的 Dst 指数以及它们在 7 天时间窗口内的孤立事件识别。可以看出，它们可以分为两类。第一种类型显示了 Dst 最小值附近的高能粒子通量的显着变化和高能 (>1.5 MeV) 下的通量增加，而第二种类型仅显示 Dst 最小值附近的通量增加，而高能时的通量却没有增加。与第二种类型的风暴相比，第一种类型的风暴与更剧烈但持续时间较短的太阳风参数变化有关。一场风暴不属于任一类别，表现出两种风暴类型的特征。此外，我们研究了超相对论电子的不可逾越的障碍是否也适用于极端地磁条件。对于最高的分析能量，获得的势垒 L 壳不会低于 2.6，与之前的发现一致。