Rapid changes of magnetic fields associated with nighttime magnetic perturbation events (MPEs) with amplitudes |ΔB| of hundreds of nT and 5–10 min duration can induce geomagnetically induced currents (GICs) that can harm technological systems. This study compares the occurrence and amplitude of nighttime MPEs with |dB/dt| ≥ 6 nT/s observed during 2015 and 2017 at five stations in Arctic Canada ranging from 64.7° to 75.2° in corrected geomagnetic latitude (MLAT) as functions of magnetic local time (MLT), the SME (SuperMAG version of AE) and SYM/H magnetic indices, and time delay after substorm onsets. Although most MPEs occurred within 30 min after a substorm onset, ∼10% of those observed at the four lower latitude stations occurred over two hours after the most recent onset. A broad distribution in local time appeared at all five stations between 1700 and 0100 MLT, and a narrower distribution appeared at the lower latitude stations between 0200 and 0700 MLT. There was little or no correlation between MPE amplitude and the SYM/H index; most MPEs at all stations occurred for SYM/H values between −40 and 0 nT. SME index values for MPEs observed >1 h after the most recent substorm onset fell in the lower half of the range of SME values for events during substorms, and dipolarizations in synchronous orbit at GOES 13 during these events were weaker or more often nonexistent. These observations suggest that substorms are neither necessary nor sufficient to cause MPEs, and hence predictions of GICs cannot focus solely on substorms.

中文翻译：

---

在加拿大北极地区观察到的夜间磁场扰动事件：3.发生和振幅随磁场纬度，当地时间和磁场扰动指数的变化而变化

与振幅随着夜间磁扰动事件（民企）相关联的磁场的快速变化|Δ乙| 数百nT的持续时间和5-10分钟的持续时间会感应出会损害技术系统的地磁感应电流（GIC）。本研究将夜间MPE的发生和幅度与| d B / d t进行了比较。| 在2015年和2017年期间，在加拿大北极地区的五个站点观测到的校正地磁纬度（MLAT）为64.7°至75.2°时，≥6 nT / s是当地磁性时间（MLT），SME（SuperMAG版本的AE）和SYM的函数/ H磁指数，以及亚暴爆发后的时间延迟。尽管大多数MPE发生在亚暴爆发后30分钟之内，但在四个低纬度站观测到的MPE约有10％发生在最近一次暴发后的两小时内。在1700和0100 MLT之间的所有五个站出现了当地时间的广泛分布，在0200和0700 MLT之间的低纬度站出现了较窄的分布。MPE振幅与SYM / H指数之间几乎没有相关性；所有站点上的大多数MPE发生的SYM / H值介于-40和0 nT之间。观察到的MPE的SME指数值> 最近一次亚暴发生后1小时，亚暴期间事件的SME值范围下降了一半，而在这些事件期间，GOES 13同步轨道的双极化现象更弱或更经常不存在。这些观察结果表明，亚暴既不是造成MPE的必要条件，也不是充分原因，因此对GIC的预测不能仅集中于亚暴。