Hi Rachal!

Another massive geomagnetic storm was the infamous Carrington Event of 1859. You can read more about it here

http://en.wikipedia.org/w.../Solar_storm_of_1859

When this geomagnetic storm happened, people really did not understand these kinds of events. They could observe the sunspots and solar flares through telescopes, watch the aurora or northern lights, and make crude measurements of magnetic disturbances on the ground, but they lacked key information about geomagnetic storms and solar storms that only became available 100 years later when we started launching satellites. Because the measurements available in the 1850s were very limited, it is difficult to rank this storm on the scales we use for space weather today. However, it does appear that if a storm like the Carrington Event were to happen today it could cause serious disruptions to satellites and electrical systems on Earth.

Kris