DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model
DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model
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DOI：
10.1186/s40623-015-0274-3
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发表时间：
2015-07-22
影响因子：
3
通讯作者：
Toffner-Clausen, Lars
中科院分区：
文献类型：
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作者：
Finlay, Christopher C.;Olsen, Nils;Toffner-Clausen, Lars
我们介绍了 DTU 的 IGRF-12 候选场模型以及衍生它们的父场模型 CHAOS-5。 ESA Swarm 任务进行的十个月的磁场观测以及最新的地面观测站月度数据被用来补充之前用于构建 CHAOS-4 的数据源。 CHAOS-5 的内部场部分（我们的 IGRF-12 候选模型是从中提取的）与时间相关，球谐次数高达 20，并且涉及节间距为 0.5 年的六阶样条。在 CHAOS-5 中，与 CHAOS-4 相比，我们仅更新低度内场模型（1 至 24 度）和相关的外场模型。高度内场（25至90度）取自CHAOS-4h的同一模型，基于CHAOS-4中使用的低空CHAMP数据。我们发现CHAOS-5能够一致地拟合来自六颗独立的低地球轨道卫星的磁场数据：Orsted、CHAMP、SAC-C和三颗Swarm卫星（A、B和C）。它还充分描述了地面天文台测量的长期变化。因此，CHAOS-5 有助于对 Swarm 磁数据的质量进行初步验证，特别是证明 Swarm 矢量场数据的 Huber 加权均方根模型残差低于 Orsted 和 CHAMP 矢量数据的残差（当一台或两台星相机运行时）。 CHAOS-5显示了过去十年中核心表面的三个长期加速度脉冲； 2006年和2009年的豆类此前已有记录，但2013年的豆类最近才被确定。 2013 年脉冲在大西洋区域下方核心表面的空间特征最强，与 2006 年脉冲密切相关，但与 2009 年脉冲反相关。
We present DTU's candidate field models for IGRF-12 and the parent field model from which they were derived, CHAOS-5. Ten months of magnetic field observations from ESA's Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. The internal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, compared with CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based on low-altitude CHAMP data, which was used in CHAOS-4.We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites: Orsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variation measured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarm magnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data are lower than those to Orsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5 shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013 pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.