MNRAS vol. 20, Issue 1, November 1859, Pages 13–15 (https://doi.org/10.1093/mnras/20.1.13), containing the original report of the Carrington Event. This event in September 1859, caused by a coronal mass ejection from the Sun during solar cycle 10, resulted in widespread disruption to telegraph systems and aurorae seen as far south as the Caribbean. A solar storm of similar magnitude occurring today would be expected to cause extended blackouts and significant damage to the electrical grid.
Royal Astronomical Society