Table1_Regional character of geomagnetic field directional circularity: Holocene Eastern North America.XLS

This study characterizes the paleomagnetic secular variation (PSV) in five Holocene records from Eastern North America. We have determined equi-spaced (100-year) declination and inclination time series for the five sites and compared their directional variability. We note ten correlatable features in both inclination and declination, which indicate that these five PSV records all lie within the same PSV region. We focus on clockwise or counter-clockwise looping of paleomagnetic directions (termed circularity) in these PSV records. We have used two techniques to estimate the circularity. We have first calculated the rate and direction of motion in 200-year intervals for each record. We have also looked for discernable looping (full loops down to 1/2 loops) in individual records. We estimate the loop sizes, durations, and circularity direction. We note the same pattern of circularity in both methods. There are seven intervals of alternating circularity in all five sites. They normally agree in timing and direction of circularity. Both methods suggest an alternating, teeter-totter like, behavior to PSV circularity. This teeter-totter behavior is unbalanced with more time spent in counter-clockwise motion than in clockwise motion. The loops have a distribution of sizes and durations with smaller loops being shorter in duration (400–800 years) and bigger loops having longer durations (600–1,200 years). The teeter-totter alternation of clockwise versus counter-clockwise circularity is distinctive and may be a normal aspect of PSV. The alternation is not consistent with several traditional ideas about fluid flow (drift, whirling motion, simple convection) in the outer core. Recent studies have identified torsional oscillations as a source for both historical short-term (decadal) and millennial-scale (103) secular variation. Such a pattern of fluid flow might create the alternating teeter-totter-like behavior of circularity that we see. All five PSV records also display five short (

本研究对北美东部五个全新世记录中的古地磁长期变化（PSV）进行了特征描述。我们确定了五个地点等间距（100年）的偏转和倾角时间序列，并比较了它们的方向变化。我们在倾角和偏转方向上均发现了十个可相关特征，表明这五个PSV记录均位于同一PSV区域内。我们专注于这些PSV记录中古地磁方向（称为圆周性）的顺时针或逆时针环状运动。我们采用了两种技术来估计圆周性。首先，我们计算了每个记录200年间的运动速率和方向。我们还寻找了个体记录中可辨识的环状运动（从完整环到1/2环）。我们估算了环的大小、持续时间和圆周性方向。两种方法均显示出相同的圆周性模式。在所有五个地点均存在七个交替的圆周性区间。它们在圆周性的时间和方向上通常一致。两种方法均表明PSV圆周性呈现出交替的、摇摆不定的行为。这种摇摆不定的行为在逆时针运动上花费的时间多于顺时针运动。环状运动在大小和持续时间上呈现分布，较小的环状运动持续时间较短（400–800年），较大的环状运动持续时间较长（600–1,200年）。顺时针与逆时针圆周性的摇摆不定交替具有明显的特征，可能是PSV的正常属性。这种交替与传统关于外核流体流动（漂移、涡流运动、简单对流）的几种传统观念不一致。近期研究已确定扭振振荡为历史短期（十年尺度）和千年尺度（10^3）长期变化的原因。此类流体流动模式可能产生了我们所观察到的交替摇摆不定样式的圆周性。所有五个PSV记录也显示了五个短暂的（