At https://eos.org/features/the-geomagnetic-blitz-of-september-1941 … there is an image (see above) of aurora over Iowa way back in 1941. The geomagnetic storm built up over the course of a week and illuminated the night sky leaving Allied shipping open to German submarine attack but also affected modern communications systems in Europe and the US, with telephone calls interrupting radio programmes for example.
September 1941
18 September 2016Electromagnetism