We present a new biennial record of radiocarbon (14C) measured in Danish oak. The new record covers the years 1251–1378 CE, thereby spanning the Grand Solar Minimum known as the Wolf Minimum. Two oak samples from every other year were measured at the AMS facility at Aarhus University (Denmark), resulting in an average precision of 1.4‰ for the record. Spectral analysis of the new record revealed two peaks at 27 and 9.1 years, which could indicate the Hale cycle was lengthened and the Schwabe cycle shortened during the Wolf Minimum, but it is also possible that the amplitude of the Schwabe cycle was too small to be accurately identified with the acquired precision of this record. The record was bandpass filtered to investigate the variability of the amplitude in different bands, which showed a dampening of the amplitude during the second half of the Wolf Minimum in bands centered on the Schwabe and the Hale cycle, respectively. A reconstruction of the solar modulation function, Φ, also showed a periodicity of ca. 9 years, and indicated that the Wolf Minimum was preceeded by one cycle of decreased solar activity.

中文翻译：

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极寒期太阳活动的变化——来自基于丹麦橡树的高分辨率 14C 记录的新见解

我们提出了一项新的放射性碳双年记录（14C) 在丹麦橡木中测量。新记录涵盖了公元 1251 年至 1378 年，从而跨越了被称为狼极小期的太阳极小期。每隔一年在丹麦奥尔胡斯大学的 AMS 设施测量两个橡木样品，记录的平均精度为 1.4‰。新记录的光谱分析显示在 27 年和 9.1 年有两个峰值，这可能表明在沃尔夫极小期期间，黑尔周期延长，施瓦贝周期缩短，但也有可能施瓦贝周期的幅度太小而无法测量。准确地识别与此记录的获得精度。对记录进行带通滤波以研究不同频带中幅度的变化，这表明在 Wolf 极小值的后半段期间，分别以 Schwabe 和 Hale 周期为中心的频带中的幅度有所衰减。太阳调制函数 Φ 的重建也显示出约的周期性。9 年，并表明在沃尔夫最小值之前有一个太阳活动减少的周期。