Deriving secular variation from CHAMP satellite magnetic field measurements

地磁场在时间尺度上的变化从几年到数亿年不等。在这个应用程序中，我们关注的是时间尺度的短周期结束。在这个周期范围内得到的结果可用于研究核幔耦合和地幔电导率的不均匀性。低空飞行的卫星是确定次年代际长期变化的时空分布的一个非常有力的工具。我们现在正处于致力于研究地磁场的一系列太空任务的开端。预计德国CHAMP卫星将对这一倡议作出重大贡献，该卫星定于2000年7月15日发射，设计有效寿命为5年。由于卫星测量的是所有内外场贡献的总和，因此适当分离这些部分是可靠地探测主要场长期变化的先决条件。在本提案中，我们计划利用各种场源的物理性质所带来的所有已知约束，同时对磁场的内部和外部部分进行建模。如果在这一领域没有重大进展，就不能利用新任务显著提高的分辨率来获得更好的长期变化数据。

The geomagnetic field varies on time scales from years to hundreds of millions of years. In this application we focus on the short-period end of the time scale. Results obtained in this period range can be used to investigate core/mantle coupling and inhomogeneities in mantle conductivity. A low flying satellite is a very powerful tool for determining the space/time distribution of sub-decadal secular variation. We are now at the beginning of a series of space missions dedicated to the study of the geomagnetic field. One major contribution to this initiative is expected from the German satellite CHAMP, scheduled for launch 15th July 2000 and designed for an active life of 5 years. Since satellites measure the sum of all internal and external field contributions, a proper separation of these parts is a prerequisite for a reliable detection of main field secular variation. In this proposal we plan to model the internal and external part of the magnetic field simultaneously by making use of all known constraints posed by the physical properties of the various field sources. Without significant progress in this field the markedly improved resolution of the new missions cannot be utilised for deriving better secular variation data.