Wednesday, March 19, 2014

The Carrington Event

In both science fiction and science fact much hay is made of an EMP, an electromagnetic pulse. On March 9th, 1989 a coronal mass ejection (CME) reached Earth causing a geomagnetic storm. It caused short-wave radio interference, including the disruption of radio signals from Radio Free Europe into Russia. Numerous satellites in polar Orbit lost contact with Earth. Oh, and it tripped circuit breakers on Hydro-Quebec's power grid blacking out the whole province of Quebec. It is interesting to note that there was a similar but more powerful event that happened over a century earlier. More here.

In 1859 Earth experienced what is often referred to as the "Carrington Event." It is named for the British astronomer who recorded the solar flare.  The Carrington Event is believed to have been the largest recorded solar storm ever. And while it occurred early in the era of industrialization, there was still some electrical and communications infrastructure to be disrupted.

George Bartlett Prescott reported that a 40 mile stretch of telegraph line owned by the American Telegraph Co. between South Braintree, ME and Fall River, MA worked without batteries for more than an hour or in his words "...with the aid of celestial batteries alone."  It sounds like exaggeration, but similar effects had been recorded as early as November 17th, 1848 by M Matteucci on a telegraph between Florence and Pisa in Italy. He detected electro-magnetism in the apparatus after the batteries were disconnected during the aurora borealis. Edward Highton detected a similar effect in England during the same event. In 1851 it was detected again under similar circumstances in Philadelphia by a Dr. Franklin:
"The aurora borealis visible on Wednesday and Thursday nights last, was the most brilliant and remarkable exhibition of the kind noticed here for years, and was attended with some very singular phenomena. On Wednesday morning an unusual appearance of atmospheric electricity was manifest on all the telegraph lines radiating from Philadelphia, east, west and south which continued more or less until Thursday evening.  At times there was a powerful current upon the wires, sustained for minutes, then it would diminish, and the current from the batteries, cease to have any effect on the magnet. It came not in flits and flashes, as is the case during thunder storms, but would emit a steady spark for seconds, even minutes..."
 Franklin called it atmosphereic electricity. Prescottcalled it "terrestrial magnetism" others called them telluric currents.  None yet understood the cause. Carrington was the astronomer who connected it to solar activity and CMEs. The 1859 event was larger than the previous ones.

There were numerous claims of spark discharges shocking telegraph operators. Later claims of it setting fire to telegraph paper were probably hyperbole. Though a CME in 1921 was stated to have started fires (or almost so) at several telegraph stations in Sweden. Back in 1859, the aurora borealis was reported by many sources to have extended as far south as Cuba making such outlandish claims seem strangely plausible.