BIG STEP FORWARD. “The geomagnetic activity connection to solar processes was established by mid-nineteenth century: Solar flare correlation with active, bright auroras and geomagnetic disturbances was found by Carrington in 1860, and long-term observations showed 11-year variability both in sunspot numbers and occurrence frequency of magnetic disturbances and auroras.”
https://link.springer.com/article/10.12942/lrsp-2007-1