Free Astronomy Magazine July-August 2024

8 JULY-AUGUST 2024 ASTRO PUBLISHING the link between cause and effect that the ex- traordinary geomag- netic storm (classified as “great”) he witnessed the initiation of is called the “Carrington Event.” The exceptional nature of that storm can also be attributed to the fact that it crossed the dis- tance of almost 150 mil- lion km (93 million miles) between the Sun and the Earth in just 17.6 hours, much faster than the period of a few days usually taken by CMEs to reach the Earth’s orbit. Follow-up investigations over the last 150 years point to the auro- ral displays of August 28 and 29, 1859 as indicating that a prior CME was the reason why the September C arrington House, with his observa- tory, built in 1852 on Furze Hill, Redhill, Sur- rey, UK. This drawing dates to 1857 or a few years earlier. D rawing by Carrington which portrays the ac- tive region in which, on Sep- tember 1st, 1859, the solar flare occurred (in A-B) and the following day produced the most violent geomag- netic storm of which we have evidence. The flare had a bipolar structure. The phe- nomenon remained visible for about five minutes and was found to move (in C-D) towards the west by a few degrees. Presumably, the plasma released by the flare arched over the central part of the sunspot group, ex- panding and cooling until it was indistinguishable from the underlying photosphere. merit of associating that “white light flare” (as he himself defined it) with the extraordinary events that occurred on our planet the follow- ing day: very bright auroras visible at any latitude and strong electrical interference. It is for understanding ently moving between the sunspots in the active region. Carrington’s ob- servation was confirmed by an inde- pendent observation conducted by his compatriot and fellow amateur astronomer Richard Hodgson. Un- like the latter, Carrington had the