The Earth's surface magnetic field and its secular variation (SV) are composed of several constituents, at sub-centennial (60–90 years) and inter-decadal (20–30 years) timescales, of internal origin, and at decadal (~11 years) timescale, of external origin, superimposed on a so-called inter-centennial constituent (timescale of about 400 years or larger). In this study we explore the appearance, structure, and dynamics of the SV foci from the perspective of the constituents with internal sources. Data from long time-span geomagnetic models, such as gufm1 (1590–1990) and COV-OBS (1840–2010), have been used to separate various constituents by Hodrick-Prescott (HP) and Butterworth filtering. Time-Longitude/Latitude plots, based on main field models time series on a grid of 2.5°x2.5° were constructed for various longitudes/latitudes respectively, on which a Radon transform was applied to get information on displacement in time of the constituents and of the SV foci, in the form of Latitude-Azimuthal-Speed and Longitude-Meridional-Speed power plots. The Earths surface field variability for the 400 years time-span is analyzed for the constituents of the field. Assessment of the geomagnetic field evolution at the Earth's surface and its characteristics, by our approach, revealed: (1) tendency of the westward drift of the inter-centennial constituent to the southern hemisphere, (2) absent meridional displacement of the inter-centennial constituent, (3) westward drift of the higher frequency constituents in a ± 20° equatorial band.

地球的表面磁场及其长期变化（SV）由百年以下（60–90年）和年代际（20–30年）时标，内部起源和年代际（〜11）的几个分量组成外部来源的时间标度）叠加在所谓的百年跨度成分上（时间标度约400年或更大）。在这项研究中，我们从具有内部来源的成分的角度探讨了SV病灶的外观，结构和动力学。来自长时间跨地磁模型的数据，例如gufm1Hodrick-Prescott（HP）和Butterworth过滤（1590–1990）和COV-OBS（1840–2010）已用于分离各种成分。基于主场模型的时间-经度/纬度图，分别针对各种经度/纬度在2.5°x2.5°的网格上构建了时间序列，然后在其上应用Radon变换以获取有关成分随时间变化的信息和SV焦点的形式，即纬度-方位角速度和经度-子午线速度图。分析了400年时间跨度中地球表面场的变化，以获取该场的组成部分。通过我们的研究方法评估了地球表面的地磁场演化及其特征，发现：（1）百年历史成分向南半球向西漂移的趋势，