Four centuries of geomagnetic secular variation from historical records
Four centuries of geomagnetic secular variation from historical records
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DOI：
10.1098/rsta.2000.0569
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发表时间：
2000-03-15
期刊：
影响因子：
--
通讯作者：
Walker, MR
中科院分区：
文献类型：
--
作者：
Jackson, A;Jonkers, ART;Walker, MR
本文提出了1590 ~ 1990年地核地幔边界磁场的新模型。这个名为gufm1的模型是基于对磁场历史观测的大量新汇编。新数据集的大部分来自从事商船和海军运输的海员未发表的观测结果。对于可能的定位错误（源于对经度的不了解）的数据更正和数据中错误的适当分配给予了相当大的关注。我们采用一个随机模型来处理未校正的位置误差，该模型基于布朗运动模型，适当地解释了噪声过程的性质。我们分析的航海误差随航行时间的变化与这个模型是一致的。在1800年以前，在超过64000个地点记录了83000多次磁偏角观测；仅17世纪就有8000多次新的观测。我们从数据集构建的时变场模型在空间上以球面谐波参数化，在时间上以b样条参数化，总共使用36512个参数。该模型提高了核心油田的分辨率，代表了油田最长的连续模型。然而，充分利用数据库可能需要一种新的建模方法。
We present a new model of the magnetic field at the core mantle boundary for the interval 1590-1990. The model, called gufm1, is based on a massive new compilation of historical observations of the magnetic field. The greater part of the new dataset originates from unpublished observations taken by mariners engaged in merchant and naval shipping. Considerable attention is given to both correction of data for Possible mislocation (originating from poor knowledge of longitude) and to proper allocation of error in the data. We adopt a stochastic model for uncorrected positional errors that properly accounts for the nature of the noise process based on a Brownian motion model. The variability of navigational errors as a function of the duration of the voyages that we have analysed is consistent with this model. For the period before 1800, more than 83 000 individual observations of magnetic declination were recorded at more than 64 000 locations; more than 8000 new observations are for the 17th century alone. The time-dependent field model that we construct from the dataset is parametrized spatially in terms of spherical harmonics and temporally in B-splines, using a total of 36 512 parameters. The model has improved the resolution of the core field, and represents the longest continuous model of the field available. However, full exploitation of the database may demand a new modelling methodology.