What was the Carrington Event of 1859?

The Carrington Event was the most intense geomagnetic storm in recorded history, peaking on 1 and 2 September 1859 during solar cycle 10. It produced auroral displays reported around the world and caused sparking, and even fires, in telegraph stations. It is named for the English astronomer Richard Carrington, who saw the solar flare linked to it. Sources: wikipedia.org (https://en.wikipedia.org/wiki/Carrington_Event) and the Science Museum (https://www.sciencemuseum.org.uk/objects-and-stories/how-does-space-weather-affect-earth). [1] [2]

On 1 September 1859, just before noon local time, Carrington and Richard Hodgson each independently recorded what are regarded as the first observations of a solar flare. Carrington was sketching a projected image of the Sun when a brilliant white light appeared above a large sunspot group. He first thought a ray of daylight had pierced a hole in the screen. The light was visible for about five minutes and then faded. [3] [2] [1]

The Kew Observatory magnetometers recorded a blip in Earth's magnetic field at the same time. When Carrington met Balfour Stewart, the head of Kew, they realised the two had coincided. This helped establish a link between solar activity and disturbances of Earth's magnetic field. At the time, the cause of auroras was not understood. [2] [4]

The geomagnetic storm is thought to have been caused by a coronal mass ejection, a burst of magnetized plasma, that struck Earth's magnetosphere. It is estimated to have crossed the roughly 150 million kilometres to Earth in 17.6 hours, far faster than the several days typical for such ejections. An earlier, smaller ejection around 28 and 29 August is widely believed to have cleared slowing solar wind plasma from the path. [1] [3]

Auroras appeared in both hemispheres, and the northern lights were seen farther south than had ever been recorded. Some newspapers reported that the light was bright enough to read a book by. [2] [5]

By 1859 the telegraph was an established global network, and it was badly disrupted. Strong currents in the wires shocked operators and started small fires in some offices. Some operators could send no messages, while others sent messages with their batteries disconnected, or received nonsensical messages that no one had sent. The Science Museum estimates the disruption lasted about 12 hours. Systems in Europe and North America were reported to be hit hardest. [5] [2] [3]

The sources do not describe the cause identically. The Science Museum says the bright lights Carrington saw were a coronal mass ejection. Other sources describe what he saw as a white-light solar flare, with the ejection a separate, associated event that most likely drove the storm. Estimates of the storm's strength also vary, with one source giving a range of −0.80 to −1.75 μT. [2] [3] [1]