Just a few months before the solar maximum on 1860.1, during the 10th solar cycle, many sunspots appeared on the Sun from August 28 to September 2, 1859. On August 29, southern auroras were observed as far north as Queensland, Australia. Just before noon on September 1, the English amateur astronomersRichard Carrington and Richard Hodgson independently recorded the earliest observations of a solar flare. Carrington and Hodgson compiled independent reports which were published side-by-side in the Monthly Notices of the Royal Astronomical Society, and exhibited their drawings of the event at the November 1859 meeting of the Royal Astronomical Society. The flare was associated with a major coronal mass ejection that travelled directly toward Earth, taking 17.6 hours to make the 150 million kilometer journey. Typical CMEs take several days to arrive at Earth, but it is believed that the relatively high speed of this CME was made possible by a prior CME, perhaps the cause of the large aurora event on August 29 that "cleared the way" of ambient solar windplasma for the Carrington event. Because of a geomagnetic solar flare effect observed in the Kew Observatorymagnetometer record by Scottish physicist 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 American mathematician Elias Loomis, which support the observations of Carrington and Stewart. On September 1–2, 1859, one of the largest geomagnetic storms occurred. Auroras were seen around the world, those in the northern hemisphere as far south as the Caribbean; those over the Rocky Mountains in the U.S. were so bright that the glow woke gold miners, who began preparing breakfast because they thought it was morning. People in the northeastern United States could read a newspaper by the aurora's light. The aurora was visible from the poles to low latitude areas such as south-central Mexico, Queensland, Cuba, Hawaii, southern Japan and China, and even at lower latitudes very close to the equator, such as in Colombia. Estimates of the storm strength range from −800 nT to −1750 nT. Telegraph systems all over Europe and North America failed, in some cases giving telegraph operators electric shocks. Telegraph pylons threw sparks. Some telegraph operators could continue to send and receive messages despite having disconnected their power supplies. On Saturday, September 3, 1859, the Baltimore American and Commercial Advertiser reported: In 1909, an Australian gold miner C.F. Herbert retold his observations in a letter to The Daily News in Perth:In June 2013, a joint venture from researchers at Lloyd's of London and Atmospheric and Environmental Research in the United States used data from the Carrington Event to estimate the current cost of a similar event to the U.S. alone at $0.6–2.6 trillion.
Other evidence and similar events
s containing thin nitrate-rich layers have been analysed to reconstruct a history of past solar storms predating reliable observations. Some researchers claim that data from Greenland ice cores show evidence of individual solar-proton events, including the Carrington event. More ice core work casts significant doubt on this interpretation, and shows that nitrate spikes are not a result of solar energetic particle events. Indeed, no consistency is found in cores from Greenland and Antarctica, and nitrate events can be due to terrestrial events such as burnings, so use of this technique is now in doubt. Other research has looked for signatures of large solar flares and CMEs in carbon-14 in tree rings and beryllium-10 in ice cores, finding such a signature of a large solar storm in 774 CE but finding that such events occur on average only once every several millennia. Less severe storms occurred in 1921 and 1960, when widespread radio disruption was reported. The March 1989 geomagnetic stormknocked out power across large sections of Quebec. On July 23, 2012 a "Carrington-class" solar superstorm was observed; its trajectory narrowly missed Earth.
