Localized regions of low geomagnetic intensity such as the South Atlantic Anomaly allow energetic particles from the Van Allen radiation belt to precipitate into the atmosphere and have been linked to a signature in the form of red aurora–like airglow visible to the naked eye. Smoothed global geomagnetic models predict a low-intensity West Pacific Anomaly (WPA) during the sixteenth to nineteenth centuries characterized by a simple time dependence. Here, we link the WPA to an independent database of equatorial aurorae recorded in Seoul, South Korea. These records show a complex fluctuating behavior in auroral frequency, whose overall trend from 1500 to 1800 AD is consistent with the locally weak geomagnetic field of the WPA, with a minimum at 1650 AD. We propose that the fluctuations in auroral frequency are caused by corresponding and hitherto unknown fluctuations in the regional magnetic intensity with peaks at 1590 and 1720 AD, a time dependence that has been masked by the smoothing inherent in regularized global geomagnetic models. A physical core flow model demonstrates that such behavior requires localized time-dependent upwelling flows in the Earth’s core, possibly driven by regional lower-mantle anomalies.

低地磁强度的局部区域（例如南大西洋异常）允许来自范艾伦辐射带的高能粒子沉淀到大气中，并与肉眼可见的红色极光状气辉形式的特征相关联。平滑的全球地磁模型预测了 16 至 19 世纪期间的低强度西太平洋异常 (WPA)，其特征是简单的时间依赖性。在这里，我们将 WPA 链接到韩国首尔记录的赤道极光独立数据库。这些记录显示极光频率存在复杂的波动行为，其从公元1500年到1800年的总体趋势与WPA的局部弱地磁场一致，在公元1650年达到最小值。我们认为，极光频率的波动是由区域磁场强度的相应且迄今为止未知的波动引起的，峰值出现在公元 1590 年和 1720 年，这种时间依赖性已被正则化全球地磁模型固有的平滑所掩盖。物理核心流模型表明，这种行为需要地核中出现局部随时间变化的上升流，这可能是由区域下地幔异常驱动的。