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An activity index for geomagnetic paleosecular variation, excursions, and reversals

机译：地磁古分子变异，偏移和逆转的活动指数

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摘要

Magnetic indices provide quantitative measures of space weather phenomena that are widely used by researchers in geomagnetism. We introduce an index focused on the internally generated field that can be used to evaluate long term variations or climatology of modern and paleomagnetic secular variation, including geomagnetic excursions, polarity reversals, and changes in reversal rate. The paleosecular variation index, P-i, represents instantaneous or average deviation from a geocentric axial dipole field using normalized ratios of virtual geomagnetic pole colatitude and virtual dipole moment. The activity level of the index, sigma P-i, provides a measure of field stability through the temporal standard deviation of P-i. P-i can be calculated on a global grid from geomagnetic field models to reveal large scale geographic variations in field structure. It can be determined for individual time series, or averaged at local, regional, and global scales to detect long term changes in geomagnetic activity, identify excursions, and transitional field behavior. For recent field models, P-i ranges from less than 0.05 to 0.30. Conventional definitions for geomagnetic excursions are characterized by P-i exceeding 0.5. Strong field intensities are associated with low P-i unless they are accompanied by large deviations from axial dipole field directions. sigma P-i provides a measure of geomagnetic stability that is modulated by the level of PSV or frequency of excursional activity and reversal rate. We demonstrate uses of P-i for paleomagnetic observations and field models and show how it could be used to assess whether numerical simulations of the geodynamo exhibit Earth-like properties.
机译：磁指数提供了地磁研究人员广泛使用的空间天气现象的定量测量。我们介绍一个专注于内部生成的领域的指数，可用于评估现代和古磁性异常变化的长期变化或气候学，包括地磁偏移，极性逆转和逆转率的变化。古分子变化指数p-i表示使用虚拟地磁杆菌落和虚拟偶极矩的标准化比率与地区轴向偶极场的瞬时或平均偏差。索引Sigma P-I的活动水平，通过P-I的时间标准偏差提供了现场稳定性的量度。可以在来自地磁场模型的全局网格上计算P-I，以揭示场结构的大规模地理变化。可以在各个时间序列中确定，或者在本地，区域和全球范围内进行平均，以检测地磁活动的长期变化，识别短途旅行和过渡现场行为。对于最近的现场模型，P-I范围为小于0.05至0.30。用于地磁偏移的常规定义是P-I超过0.5的特征。强的场强度与低P-I相关联，除非它们伴随着与轴向偶极场方向的大偏差。 Sigma P-I提供了由PSV水平或远潜活动的频率调节的地磁稳定性的衡量标准和逆转率。我们展示了P-I的用途，用于古磁性观测和现场模型，并展示如何用于评估Geodynamo的数值模拟是否表现出地球状性质。

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