Enhanced precipitation of magnetospheric energetic electrons during substorms increases ionospheric electron density and conductance. Such enhancements, which have timescales of a few hours, are not reproduced by the existing ionospheric models. We use the linear prediction filter (LPF) method to reconstruct the substorm-related response of electron densities and integral conductances from long-term ionospheric observations made by the European Incoherent SCATer radar located at Tromsø. To characterize the intensity of substorm dipolarization at a 5 min time step, we use the midlatitude positive bay index. We build response functions (LP filters) as a function of substorm time between T₀−1 h and T₀ + 4 h (T₀ is a substorm onset time) in different magnetic local time (MLT) sectors to estimate the magnitude and delays of the ionospheric density response at different altitudes. Systematic and large relative changes are mostly observed in the D- and E regions. The duration of the response is about 3 h. It starts and reaches maximum magnitude near midnight, propagating from there toward the east and decaying after passing into the noon-evening sector. The reliability of LPF results is confirmed by the consistency of D-region response with independently derived response of the auroral absorption. Whereas strong ionization increases are seen in both E- and D-regions on the nightside, the D-region response is stronger in the morning-dayside sector. Such MLT variation corresponds to the drift motion and precipitation of the high-energy electrons injected in the nightside magnetosphere during substorm dipolarization. The inferred ionization changes result in strong enhancements of integral Hall (and Pedersen) conductance in the nightside auroral zone, where intense auroral currents are known to occur during substorms

中文翻译：

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亚暴期间极光区电离层电子密度和电导的变化

亚暴期间磁层高能电子的增强降水增加了电离层电子密度和电导。现有的电离层模型无法再现这种具有几个小时时间尺度的增强。我们使用线性预测滤波器 (LPF) 方法从位于特罗姆瑟的欧洲非相干 SCATer 雷达进行的长期电离层观测中重建电子密度和积分电导的亚暴相关响应。为了表征 5 分钟时间步长的亚暴双极化强度，我们使用中纬度正海湾指数。我们构建响应函数（LP 滤波器）作为 T ₀ −1 h 和 T ₀ + 4 h (T ₀是亚暴开始时间）在不同的磁本地时间（MLT）扇区中，以估计不同高度电离层密度响应的幅度和延迟。系统性和较大的相对变化主要发生在 D 区和 E 区。响应持续时间约为 3 小时。它在午夜附近开始并达到最大震级，从那里向东传播，并在进入午晚扇区后衰减。LPF 结果的可靠性通过 D 区响应与独立导出的极光吸收响应的一致性得到证实。虽然在夜间的 E 区和 D 区都看到了强烈的电离增加，但在早晨的白天部门，D 区的反应更强。这种 MLT 变化对应于亚暴双极化期间注入夜侧磁层的高能电子的漂移运动和降水。推断的电离变化导致夜侧极光区的积分霍尔（和佩德森）电导强烈增强，已知在亚暴期间会发生强烈的极光电流