Abstract. A set of 24 isolated, 46 compound and 36 multi-night substorm events from the years 2008–2013 have been analysed in this study. Isolated substorm events are defined as single expansion-recovery phase pairs, compound substorms consist of multiple phase pairs, and multi-night substorm events refer to recurring substorm activity on consecutive nights. Approximately 200 nights of substorm activity observed over the Fennoscandian Lapland have been analysed for their magnetic disturbance magnitude and the level of cosmic radio noise absorption. Substorm events were automatically detected from the local electrojet index data and visually categorised.

We show that isolated substorms have limited lifetimes and spatial extents, as compared to the other substorm types. The average intensity (both in absorption and ground-magnetic deflection) of compound and multi-night substorm events is similar. For multi-night substorm events, the first night is rarely associated with the strongest absorption. Instead, the high-energy electron population needed to cause the strongest absorption builds up over 1–2 additional nights of substorm activity. The non-linear relationship between the absorption and the magnetic deflection at high and low activity conditions is also discussed. We further collect in-situ particle spectra for expansion and recovery phases to construct median precipitation fluxes at energies from 30 eV up to about 800 keV. In the expansion phases the bulk of the spectra shows a local maximum flux in the range of a few keV to 10 keV, while in the recovery phases higher fluxes are seen in the range of tens of keV to hundreds of keV. These findings are discussed in the light of earlier observations of substorm precipitation and their atmospheric effects.

中文翻译：

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在孤立，复合和多夜亚暴事件中的电子降水特征

摘要。本研究分析了2008-2013年间发生的24个孤立，46个复合和36个多夜亚暴事件。孤立的亚暴事件定义为单个膨胀-恢复阶段对，复合亚暴包括多个阶段对，而多夜亚暴事件是指连续夜重复发生的亚暴活动。对芬诺斯堪的拉普兰地区观察到的大约200晚亚风暴活动进行了分析，分析了它们的磁干扰强度和宇宙无线电噪声吸收水平。从当地的电喷指数数据中自动检测到亚暴事件，并对其进行视觉分类。

我们显示，与其他亚暴相比，孤立的亚暴具有有限的寿命和空间范围。复合和多夜亚暴事件的平均强度（在吸收和地磁偏转中）相似。对于多夜的亚暴事件，第一夜很少与最强的吸收相关。取而代之的是，引起最强吸收所需的高能电子种群会在亚暴活动的额外1-2个晚上建立起来。还讨论了在高和低活度条件下吸收与磁偏转之间的非线性关系。我们进一步收集用于膨胀和恢复阶段的原位粒子光谱，以构建能量从30 eV到大约800 keV的中值降水通量。在膨胀阶段，大部分质谱图显示了在几keV至10 keV范围内的局部最大通量，而在恢复阶段，观察到较高的通量在几十keV至数百keV的范围内。这些发现是根据较早的亚暴雨降水及其大气影响的观测结果进行讨论的。