The solar cycle represents the Sun’s periodically changing magnetic state, which is potentially subject to global magnetic anomalies emerging on it. What the characteristics are of the Sun’s large-scale magnetic field playing roles in these anomalies is a key to clarifying how the Sun deviates from its normal magnetic state. This article reports aggregation characteristics of the large-scale magnetic field associated with a global magnetic anomaly that emerged when the Sun went through one of the longest solar cycles in two hundred years. The characteristics were identified by extracting cluster feature values of solar surface magnetic fields via a population ecological method from synoptic maps, obtained by the longest homogeneous series of magnetic field observations for the past several decades. We found that the anomaly was due to the uneven clustering of positive and negative surface magnetic fields that occurred during the solar minimum leading to the last extended solar cycle. Our findings may provide new insight into magnetic field characteristics peculiar to a solar minimum with an extended cycle length.

太阳周期代表太阳周期性变化的磁态，这有可能受到其上出现的整体磁异常的影响。太阳的大磁场在这些异常中起什么作用，这是弄清太阳如何偏离其正常磁态的关键。本文报道了与全球磁场异常有关的大规模磁场的聚集特征，这种异常现象是在太阳经历了200年中最长的太阳周期之一时出现的。通过人口生态学方法从天气地图中提取太阳表面磁场的簇特征值来识别特征，该天气图是过去几十年中最长的均匀磁场观测序列获得的。我们发现异常是由于正负表面磁场在太阳最小值期间发生的不均匀聚集引起的，从而导致最后一个太阳周期的延长。我们的发现可能会提供新的洞察力，以了解太阳极小特有的磁场特性（具有更长的循环长度）。