Separating multi-decadal internal geomagnetic secular variation and magnetospheric field variations

分离数十年内部地磁长期变化和磁层场变化

• 批准号: 273423638
• 负责人: Dr. Monika Korte
• 金额: --
• 依托单位: Sektion 2.3: Geomagnetismus
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/273423638?language=en
• 关键词: Separating; multi; decadal; internal; geomagnetic

The magnetic core field and its magnetosphere show relevant changes on time scales from hours (magnetic storms) to millions of years (polarity reversals). Geomagnetic observations contain contributions from: the main field produced by geodynamo processes in Earth's outer core; the lithospheric field from magnetized rocks and geological structures; and highly variable fields caused by current systems in ionosphere and magnetosphere with secondary fields from induction in conductive structures in the Earth's crust and mantle. Separation of the different contributions is essential to understand the underlying processes with implications for future main field evolution, space weather conditions or interpretation of lithospheric anomalies. This separation remains a challenge. Modern vector magnetic field satellite data lead to increasingly accurate geomagnetic main-field models that co-estimate large-scale magnetospheric fields. When using geomagnetic observatory time series for internal field secular variation studies external field variations and their induced counterparts are traditionally filtered out by using monthly or annual mean values. Comparisons of the modern models to such data confirm that multi-annual to decadal magnetospheric variations are present in these time series, which are essential to investigate internal secular variation and characteristics of main field evolution on a wider frequency range than available from satellite data. Geomagnetic activity indices like the Dst (disturbed storm time) index were developed to describe magnetospheric field variations. The Dst index by design does not describe long-term variations correctly. A number of improvements to Dst have been suggested, but none of them has specifically addressed the decadal stability and absolute level. This project aims to derive a method to better separate the multi-annual to decadal magnetospheric field variations and internal secular variation from geomagnetic observatory and repeat station time series. We will take advantage of the global data compilations of ground data available from the World Data Center Edinburgh and the results from separating internal and magnetospheric fields in the modern models based on data from the satellites CHAMP, Ørsted and Swarm (in particular including new findings obtained within this SPP) to develop a new magnetospheric and induced counterpart index using ground data, that can be extended back to the early 20th century. The benefits will be twofold: Firstly, an improved understanding of long-term magnetospheric variations is important, e.g., regarding space weather implications. Secondly, cleaner internal field ground data will enable more detailed studies of decadal secular variation and core field characteristics to better understand core dynamics and geodynamo processes and will also facilitate the use of repeat station data to augment total field lithospheric anomaly mappings with vector field information.

磁芯场及其磁层显示出从小时（磁场）到数百万年（极性逆转）的时间尺度上的相关变化。地磁观测值包含：地球外部芯中Geodynamo过程产生的主要领域的贡献；来自磁化岩石和地​​质结构的岩石圈场；以及由电离层和磁层中的电流系统引起的高度可变场，其次级磁场来自地壳和地幔中导电结构的次级磁场。不同贡献的分离对于了解对未来主要田间进化，太空天气条件或岩石圈异常的解释的影响至关重要。这种分离仍然是一个挑战。现代矢量磁场卫星数据导致越来越准确的地磁主要场模型，这些模型共构成了大规模磁场。当使用地磁观察时间序列进行内部田间世俗变化研究时，外部田间变化及其诱导的对应物传统上会通过每月或年平均值来滤除。现代模型与此类数据的比较证实，这些时间序列中存在多年度至际磁层变化，这对于研究内部世俗变化和主场进化的内部世俗变化和比卫星数据中可用的更广泛频率范围至关重要。开发了诸如DST（干扰风暴时间）指数之类的地磁活动指数来描述磁层场的变化。设计的DST索引无法正确描述长期变化。已经提出了一些对DST的改进，但没有一个专门解决了际稳定性和绝对水平。该项目旨在得出一种方法，以更好地将多年至际磁层场变化和内部世俗变化与地磁观察和重复站时间序列分开。 We will take advantage of the global data compilations of ground data available from the World Data Center Edinburgh and the results from separating internal and magnetosphere fields in the modern models based on data from the satelites CHAMP, Ørsted and Swarm (in particular including new findings obtained within this SPP) to develop a new magnetosphere and induced counterpart index using ground data, that can be extended back to the early 20th century.好处将是双重的：首先，对长期磁层变化的改进理解很重要，例如，关于空间天气的影响。其次，清洁剂的内部场地数据将使对际际世俗变化和核心场特征进行更详细的研究，以更好地了解核心动力学和地球人物过程，还将促进使用重复站数据来增强使用矢量场信息的总场岩石圈异常映射。