Fig. 1
![Fig. 1](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40623-022-01581-x/MediaObjects/40623_2022_1581_Fig1_HTML.png)
The locations of the used ground-based observation stations. The curved dashed and solid lines represent the geomagnetic latitudes. The GNSS, ionosonde, and magnetometer stations are illustrated with red, black, and blue triangles, respectively