An astronomer's private view
On the morning of September 1, 1859, Richard Carrington, a wealthy amateur astronomer, was in his private observatory in Redhill, Surrey. He was projecting an image of the sun through his telescope and sketching a large group of sunspots when he saw something unprecedented. At 11:18 AM, he witnessed two "patches of intensely bright and white light" suddenly erupt from the sunspot group. The event was so brilliant he initially thought there was a hole in his viewing screen letting daylight through. Realizing he was observing a solar phenomenon, he ran to find someone to witness it with him, but when he returned 60 seconds later, the lights were already fading. The entire observation lasted only five minutes. Another English astronomer, Richard Hodgson, independently recorded the same event, confirming it was not an instrumental error. This was the first time in history a solar flare had been observed and documented.
The eruption Carrington saw was a white-light flare, a particularly rare and energetic type. Modern analysis estimates its X-ray classification was around X45, making it one of the most powerful flares ever recorded. The flare hurled a colossal cloud of magnetized plasma, known as a coronal mass ejection (CME), directly at Earth. This CME traveled the 93 million miles (150 million km) from the Sun to Earth in a record 17.6 hours; a trip that typically takes several days. Carrington suspected a link between the solar event and subsequent terrestrial disturbances, an important for the field of space weather.
A planet electrified
The arrival of the CME triggered the most intense geomagnetic storm in recorded history, now called the Carrington Event. The storm's effects on the planet's magnetosphere were immediate and dramatic. Telegraph systems, the pinnacle of mid-19th-century technology, failed across North America and Europe. The geomagnetically induced currents were so powerful that telegraph pylons threw sparks and the paper in receivers spontaneously combusted. Some operators received electric shocks from their equipment. Demonstrating the storm's power, operators in Boston found they could disconnect their batteries and still transmit messages to Portland, Maine, using only the current induced by the aurora.
The storm also produced spectacular auroras, seen across the globe. The northern lights were so bright over the Rocky Mountains that gold miners woke up and started making breakfast, thinking it was morning. People in the northeastern United States could read newspapers by the aurora's light. Normally confined to polar regions, the auroral displays were witnessed as far south as Cuba, Hawaii, and even Colombia, which is near the equator. Ice core samples suggest the Carrington Event was twice as large as any other solar storm in the last 500 years. If a storm of this magnitude occurred today, it would cause widespread disruptions to power grids, satellite communications, and GPS systems.