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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The 2003 geomagnetic jerk and its relation to the core surface flows
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The 2003 geomagnetic jerk and its relation to the core surface flows

机译：2003年地磁急动及其与核心地表流的关系

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In this paper we examine the core surface flow obtained by an inversion of a continuous model of the geomagnetic field and its temporal variation using the diffusion-less induction equation. The continuous CHAOS model is derived from satellite data up to spherical harmonic degree 14 and covers the period 1999 to 2006. The CHAOS secular variation, when downward continued to the core surface, shows stripe-like features, which can be attributed to spherical harmonic degree 12 and higher. These contributions are removed by applying a tapering method, and the resulting tapered model is then inverted for the core surface flow. Satellite-based field models have a high spatial resolution; however, their temporal resolution is limited. In order to enhance the temporal resolution of the flow, we additionally constrain the flow to fit the secular variation from ground-based observatory data. A range of solutions, subject to different constraints, are computed, two flow hypotheses being considered: purely toroidal flow and tangentially geostrophic flow. We show that both flow types provide similar results; however, the purely toroidal flow provides a better fit to the secular variation in the equatorial region than the tangentially geostrophic flow. We then analyze the residuals between observed secular variation and its predictions from the flow. We note larger residuals for the tangentially geostrophic flow, where strong radial secular variation and a weak radial field are observed. Although diffusive effects cannot be ruled out as a potential source of the mismatch, we attribute the larger residuals to be caused by a flawed estimation of the poloidal flow. We also seek to relate temporal changes in the fluid flow to the geomagnetic jerk which occurred at the beginning of 2003. It is found that this geomagnetic jerk coincides with variations in the zonal flow components of both flow types, suggesting a possible link to torsional oscillations. However, we argue that other flow components are important to obtain a detailed fit of the observed secular variation. Finally, we compare observed changes in the length-of-day and the predictions from the flow solutions.
机译：在本文中，我们研究了通过使用无扩散感应方程反演地磁场连续模型及其时间变化而获得的岩心表面流。连续的CHAOS模型是从卫星数据得出的，直到球形谐波度14为止，涵盖了1999年到2006年。当向下延伸到核心表面时，CHAOS的长期变化显示出条纹状特征，这可以归因于球形谐波度。 12及更高。通过应用逐渐变细的方法可以消除这些影响，然后将所得的锥形模型反转以用于岩心表面流动。基于卫星的场模型具有很高的空间分辨率。但是，它们的时间分辨率有限。为了提高流量的时间分辨率，我们还对流量进行了约束，以适应地面观测数据的长期变化。计算了受不同约束条件约束的一系列解决方案，其中考虑了两个流动假设：纯环形流动和切向地转流。我们显示两种流类型都提供相似的结果。然而，与切向地转流相比，纯环形流能更好地适应赤道地区的长期变化。然后，我们分析观察到的长期变化与其从流量预测中得出的残差。我们注意到在切向地转流中存在较大的残差，在该处观察到较强的径向长期变化和较弱的径向场。尽管不能排除扩散效应是不匹配的潜在原因，但我们将较大的残差归因于对极向性流的错误估计。我们还试图将流体流动的时间变化与2003年初发生的地磁急动联系起来。发现该地磁急动与两种流动类型的纬向流分量的变化相吻合，表明可能与扭转振荡有关。但是，我们认为其他流量分量对于获得观测到的长期变化的详细拟合很重要。最后，我们比较了一天中观察到的变化和流量解决方案中的预测。

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