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.