Stratified multifractal magnetization and surface geomagnetic fields—I. Spectral analysis and modelling
Stratified multifractal magnetization and surface geomagnetic fields—I. Spectral analysis and modelling
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DOI：
10.1111/j.1365-246x.2001.00344.x
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发表时间：
2001-04
影响因子：
2.8
通讯作者：
S. Lovejoy;S. Pecknold;D. Schertzer
中科院分区：
文献类型：
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作者：
S. Lovejoy;S. Pecknold;D. Schertzer
摘要地磁场的尺度模型试图捕捉地球系统中普遍存在的强烈和大范围的可变性。不幸的是，它们通常既是各向同性的(自相似的)，也是单裂性的(非间歇性的、准高斯的)。在这篇两篇系列论文的第一篇中，我们取消了第一个限制，认为各向异性标度对于考虑地球分层及其后果是必不可少的。特别是，在几千公里以下的水平尺度上，我们用各向异性标度来模拟薄的或居里深度受限的地壳磁化和相应的表面磁场(B)。结果表明，它一般会产生一种新的中间尺度(“红噪声”)地表B场域，在数量上与两组区域地表B场域观测的结果非常接近。这种比例不可能用标准的自相似模型来解释。利用这些数据以及水平和垂直磁化率数据，我们估计了模型的基本参数，并表明该模型与现有数据是一致的。在文2中，我们解除了单分裂的限制，进行了多重分形分析；然后，我们将各向异性标度模型扩展到包括多重分形B场和磁化场。
Summary Scaling models of geofields attempt to capture the strong and wide-range variability ubiquitous in geosystems. Unfortunately, they are generally both isotropic (self-similar) and monofractal (non-intermittent, quasi-Gaussian). In this first paper of a two-paper series, we lift the first of these restrictions, arguing that anisotropic scaling is essential for taking into account the stratification of the Earth and its consequences. In particular, at horizontal scales below several thousand kilometres we model the thin or Curie-depth-limited crustal magnetization and the corresponding surface magnetic field (B) by using anisotropic scaling. We show that it generically gives rise to a new intermediate scaling (‘red noise’) surface B field regime quantitatively very close to that observed on two sets of regional surface B field surveys. This scaling is impossible to explain using standard self-similar models. Using these data as well as horizontal and vertical susceptibility data, we estimate the basic model parameters and show that that model is compatible with the available data. In Paper II we lift the monofractal restriction and perform multifractal analyses; we then extend the anisotropic scaling model to include multifractal B and magnetization fields.