The Carrington Event: History’s Greatest Solar Storm

On this day in 1859,  the most intense geomagnetic storm in recorded history began.

From Space.Com

By Daisy Dobrijevic, Andrew May

Extreme solar storms such as the 1859 Carrington Event can play havoc with technology on Earth.

The Carrington Event was a large solar storm that took place at the beginning of September 1859, just a few months before the solar maximum of 1860.

In August 1859, astronomers around the world watched with fascination as the number of sunspots on the solar disk grew. Among them was Richard Carrington, an amateur skywatcher in a small town called Redhill, near London in England.

On Sep. 1, as Carrington was sketching the sunspots, he was blinded by a sudden flash of light. Carrington described it as a "white light flare" according to NASA spaceflight(opens in new tab). The whole event lasted about five minutes.

The flare was a major coronal mass ejection (CME), a burst of magnetized plasma from the sun's upper atmosphere, the corona. In 17.6 hours, the CME traversed over 90 million miles (150 million km) between the sun and Earth and unleashed its force on our planet. According to NASA spaceflight, it usually takes CMEs multiple days to reach Earth.

The day after Carrington observed the impressive flare, Earth experienced an unprecedented geomagnetic storm, with telegraph systems going haywire and auroral displays — normally confined to polar latitudes — visible in the tropics, according to NASA Science(opens in new tab).

Carrington put two and two together and realized that the solar flare he'd seen was almost certainly the cause of this massive geomagnetic disturbance. This was a connection that had never previously been made, according to NASA Spaceflight. The solar storm of 1859 is now known as the Carrington Event in his honor.

The origins of space weather can be traced to contortions in the sun's magnetic field, leading to dark blotches or sunspots on its surface, according to NASA Earth Observatory(opens in new tab).

It's from these spots that solar flares, coronal mass ejections and other electromagnetic phenomena can emerge — with potentially hazardous consequences for our technological way of life.

Sunspot activity rises and falls on an 11-year cycle, and we're currently approaching the next solar maximum in 2025. So now is a good time to look at the worst solar storms.

Sunspots of 1 September 1859, as sketched by Richard Carrington. A and B mark the initial positions of an intensely bright event, which moved over the course of five minutes to C and D before disappearing.