Virtual Observatories (VO-ESD) time series in Geocentric and Centred-Dipole frames

Data from "The signature of geomagnetic field external drivers from Swarm data, (Saturnino et al, 2021, submited)" Dataset consists of time series of the three geomagnetic field components at a grid of 3394 Virtual observatories (VO) in two reference frames: Geocentric (GEO) and Centred-Dipole (CD). The data for each VO is obtained from all Swam mission data between January 2014 and December 2019, acquired inside a cylinder of 2.0 degrees (about 240 km) radius centred at each VO location and during a 30-day period. Satellite data within each cylinder lie between 450 and 530 km altitude (Swarm satellite’s altitude range). The used dataset is located between -/+ 60 degrees latitude, but otherwise no data selection is applied. VOs are placed at 500 km altitude and are 3.5 degrees apart. The Equivalent Source Dipole (ESD) technique is used to estimate a magnetic field value at each VO location and for each 30-day period (Saturnino et al., 2018). The magnetic field of internal origin (n ≤ 13) as given by the CHAOS-6 model (Finlay et al., 2016, version CHAOS-6-x9) was subtracted from the VO time series, in order to isolate the external contribution. In the CD rotated frame, the rotation was made prior to the choice of the VOs grid, and the VOs were then distributed along latitude bands relative to the CD instead of the GEO equator. Only then, was the ESD inversion applied.本数据集源自《基于Swarm卫星数据的地磁外部驱动特征》（Saturnino等人，2021年，已投稿）。数据集包含3394个虚拟天文台（Virtual observatories, VO）构成的网格下的三个地磁分量时间序列，采用两种参考框架：地心坐标系（Geocentric, GEO）与中心偶极坐标系（Centred-Dipole, CD）。每个VO对应的数据取自2014年1月至2019年12月间的全部Swarm任务数据，筛选条件为以该VO位置为中心、半径2.0度（约240公里）的圆柱区域内，且处于30天时段内的卫星观测数据。该圆柱区域内的卫星数据对应轨道高度介于450至530公里（Swarm卫星的轨道高度范围）。所用数据集的纬度覆盖范围为±60度，未施加其他数据筛选规则。VO均设置于500公里高度，相邻VO间距为3.5度。采用等效源偶极（Equivalent Source Dipole, ESD）技术，针对每个VO位置与每个30天时段估算磁场数值（Saturnino等人，2018）。为分离地磁外部贡献，从VO时间序列中移除了CHAOS-6模型（Finlay等人，2016，版本CHAOS-6-x9）给出的内源磁场（n≤13）。在CD旋转坐标系中，需先完成坐标旋转再构建VO网格，且VO沿相对CD偶极的纬度带而非GEO赤道分布，之后再应用ESD反演算法。