In 1859 a Solar Storm Made Telegraphs Run on No Power and Auroras Reach Cuba

Around 11:18 a.m. on September 1, 1859, the British astronomer Richard Carrington was sketching a sunspot group at his private observatory in Surrey when two patches of intense white light suddenly bloomed across the surface of the sun. He fetched a witness, watched the patches dim and disappear over five minutes, and noted the time. He had just made the first scientific observation of a solar flare. Seventeen hours and forty minutes later, the coronal mass ejection associated with the flare arrived at Earth.

What happened next is still the standard reference event for space weather. Auroras reddened the sky as far south as Havana, Honolulu, Panama, and Queensland — gold miners in Colorado packed up their gear, thinking it was dawn. In the northeastern United States, people reported being able to read newspapers outdoors at midnight. The geomagnetic storm induced enormous currents in the world's young telegraph network. Wires sparked in offices and started fires; some operators disconnected their batteries entirely and continued sending messages purely on the current the storm was inducing in their lines. A pair of operators in Boston and Portland conversed for around two hours that way.

A Lloyd's of London study estimated in 2013 that a Carrington-class storm hitting today's electrical grid would do something between $600 billion and $2.6 trillion in damage in the United States alone. Carbon-14 spikes in tree rings suggest the 774–775 CE "Miyake event" was an order of magnitude larger than 1859.