From August 28, 1859, until September 2, numerous sunspots and solar flares were observed on the sun. Just before noon on September 1, the British astronomer Richard Carrington observed the largest flare,[3] which caused a major coronal mass ejection (CME) to travel directly toward Earth, taking 17 hours. Such a journey normally takes three to four days. This second CME moved so quickly because the first one had cleared the way of the ambient solar wind plasma.[3]
On September 1, 1859, Carrington and Richard Hodgson, another English amateur astronomer, independently made the first observations of a solar flare. Because of a simultaneous "crochet" observed in the Kew Observatory magnetometer record by Balfour Stewart and a geomagnetic storm observed the following day, Carrington suspected a solar-terrestrial connection. Worldwide reports on the effects of the geomagnetic storm of 1859 were compiled and published by Elias Loomis which support the observations of Carrington and Balfour Stewart.
On September 1–2, 1859, the largest recorded geomagnetic storm occurred. Aurorae were seen around the world, even over the Caribbean; those over the Rocky Mountains were so bright that their glow awoke gold miners, who began preparing breakfast because they thought it was morning.[3] People who happened to be awake in the northeastern US could read a newspaper by the aurora's light.[4]
Telegraph systems all over Europe and North America failed, in some cases shocking telegraph operators.[5] Telegraph pylons threw sparks and telegraph paper spontaneously caught fire.[6] Some telegraph systems continued to send and receive messages despite having been disconnected from their power supplies.[7]
On September 3, 1859, the Baltimore American and Commercial Advertiser reported, "Those who happened to be out late on Thursday night had an opportunity of witnessing another magnificent display of the auroral lights. The phenomenon was very similar to the display on Sunday night, though at times the light was, if possible, more brilliant, and the prismatic hues more varied and gorgeous. The light appeared to cover the whole firmament, apparently like a luminous cloud, through which the stars of the larger magnitude indistinctly shone. The light was greater than that of the moon at its full, but had an indescribable softness and delicacy that seemed to envelop everything upon which it rested. Between 12 and 1 o'clock, when the display was at its full brilliancy, the quiet streets of the city resting under this strange light, presented a beautiful as well as singular appearance."[8]
[edit]Similar events

Ice cores contain thin nitrate-rich layers that can be analyzed to reconstruct a history of past events before reliable observations; the data from Greenland ice cores was gathered by Kenneth G. McCracken[9] and others. These show evidence that events of this magnitude—as measured by high-energy proton radiation, not geomagnetic effect—occur approximately once per 500 years, with events at least one-fifth as large occurring several times per century.[10] Less severe storms have occurred in 1921 and 1960, when widespread radio disruption was reported.
[edit]See also

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