Time-Space Multiscale Separation of Ocean Tide Generated Magnetic Signals

在Tyler等人(2003)的CHAMP数据中首次观测到M2潮汐信号后，洋流产生的磁场在过去几年中受到了越来越多的关注。洋流产生场是继核心场/主场、电离层/磁层场和岩石层场之后，目前尚未建模的地磁场的最大贡献者。由海洋潮汐产生的部分特别令人感兴趣，因为它的时间周期性提供了将其与其他信号区分开来的可能性。然而，就在最近，Sabaka和Lesur的两项独立研究(尚未发表)可以从CHAMP数据中分离出由半日M2海潮引起的磁场，并将其与基于感应方程的模型预测相匹配。其他任何潮汐模式(如日O1潮)尚未在卫星数据中识别，主要是因为它们被具有类似时间周期的更强的电离层/磁层信号伪装。本项目的目的是使用时空多尺度方法更详细地了解海潮产生的磁场以及它们与其他地磁信号的区别。我们计划开发新的工具，基于这样一个事实，即这些磁场只起源于空间受限的海洋，因此预计将揭示与其起源的信号不同的时空结构，例如在电离层/磁层。这种方法不仅考虑了海潮的时间变化(就像所有最近的研究所做的那样)，而且还考虑了特定的空间特征，有望改善海潮产生的磁信号与卫星测量的分离。从长远来看，这些工具不仅可以用于海潮，也可以用于一般的非潮汐海洋流动。此外，更好地定量了解海潮产生的磁场将有助于改进地球电导率模型，改进对海洋污染物的岩石圈磁场模型的校正，并最终可靠地分离海潮信号，从而能够根据卫星磁场测量对实际潮汐洋流进行远程推断。这不仅使地磁学家感兴趣，而且也使海洋学和大地测量界感兴趣，解决了优先计划“地球动力”的跨学科性质。

Ocean flow generated magnetic fields have seen a growing interest in the last years, even more so, after M2 tidal signals have been observed for the first time in CHAMP data by Tyler et al (2003). Following the core/main field, the iono-/magnetospheric field, and the lithospheric field, the ocean flow generated field is now the largest unmodelled contributor to the geomagnetic field. The part that is generated by ocean tides is particularly interesting since its time periodic nature supplies a possibility to distinguish it from other signals. However, it is just recently that two independent (not yet published) studies by Sabaka and Lesur could separate the magnetic field that is due to the semidiurnal M2 ocean tide from CHAMP data and match it with model predictions based on the induction equation.Any other tidal mode (such as the diurnal O1 tide) has not yet been identified in satellite data, mostly due to the fact that they are camouflaged by stronger iono-/magnetospheric signals with a similar temporal periodicity.It is the aim of this project to use spatio-temporal multiscale methods to gain a more detailed insight into ocean tide generated magnetic fields and properties that distinguish them from other geomagnetic signals. We plan to develop novel tools based on the fact that these magnetic fields originate solely in the spatially confined oceans and, therefore, are expected to reveal a different spatio-temporal structure than signals having their origin, e.g., in the iono-/magnetosphere. Such an approach will hopefully lead to an improved separation of the ocean tide generated magnetic signal from satellite measurements by not just taking the temporal variations into account (like all recent studies do) but also the specific spatial signatures.In the long run, these tools can be of use not only for ocean tides but also for general non-tidal ocean flow. Furthermore, a better quantitative understanding of the ocean tide generated magnetic fields would help to improve models of the Earth's conductivity, allow an improved correction of lithospheric magnetic field models for oceanic contaminations, and eventually, a reliable separation of the ocean tide signals would enable remote inferences from satellite magnetic field measurements on the actual tidal ocean flow. This does not only make the project interesting to the geomagnetic but as well to the oceanographic and geodetic community, addressing the interdisciplinary character of the priority programme ''DynamicEarth''.