Southern Lights

1859

Dr. John Mitchell

During the last days of August 1859, reports of spectacular displays of the Aurora Borealis and other stratospheric phenomena came from all over Europe, Asia, the Americas and elsewhere throughout the northern hemisphere, reaching almost to the equator. Similar reports came from Australia and other southern hemisphere countries. As well as creating enormous public interest, these nocturnal entertainments and concurrent abnormalities of electrical and magnetic effects were closely monitored for their implications for science, engineering, navigation and telegraphic communications.

”The beautiful phenomenon called the Southern Lights or Aurora Australis has frequently been visible

of late. Last evening the spectacle was peculiarly attractive, ... spreading over almost the whole sky, dyeing the atmosphere of a bright roseate hue.”

Richard Carrington of Surrey, a highly-respected astronomer of private means who specialised in solar astronomy had, since 1853, been taking daily measurements and recordings of the appearance and behaviour of the sun when the weather permitted. Carrington had developed instruments to project a telescopically-enlarged image of the sun’s disc onto a screen from which he could sketch its features – sunspots, flares, rays and other characteristics.

On the morning of September 1, 1859 he continued his studies of the image of an abnormally large cluster of sunspots which he had been tracking from the time it had first appeared. It had grown, changed shape, and moved towards the centre of his screen as the sun slowly rotated over successive days. Carrington page 20 estimated the extent of the cluster had grown to span more than 80,000 miles(130,000km) i.e. more than ten times the diameter of the earth.

Suddenly, at 11.18 a.m., two brilliant flashes on the screen, emanating from within the sunspot cluster, obscured the adjoining details of the image. Carrington was so astounded that at first he believed some fault had leaked extraneous light through the apparatus. Finding all was intact, he quickly sought independent confirmation of the sighting, which remained at peak intensity for about a minute before diminishing over the following four to five minutes. This flash appeared to accompany an enormous solar flare, which exploded so rapidly over such a distance across the sun’s surface that he later estimated it must have travelled at more than 450,000 miles per hour.

A day or so later Carrington visited the observatory at Kew to check his records against any taken there. Unfortunately, a project then in progress at Kew of photographing the sun each fine day had not captured the 11.18 a.m. event, but exceedingly abnormal traces on automated paper tape connected to an array of sensitive magnets confirmed exactly both the time of onset and the duration of Carrington’s observations. His findings were later corroborated by recordings taken at many other stations throughout Britain and Europe. Carrington later reasoned that the magnetic effects observed at Kew must have been initiated at the same time as the visual flash, and had travelled to the earth at exactly the same speed.

This, of course, was the speed of light – 300,000km per second – which was not known with any accuracy in 1859. In other words, the event on the sun must have occurred at about 11.10 a.m. and its accompanying outburst of electromagnetic energy over a wide range of the spectrum, including visual and other wavelengths, reached the earth, 150 million kilometres distant, eight minutes later.

The burst recorded by Carrington was not the only effect of the flare which he had seen. Even though the magnetometers at Kew had begun to settle down a few minutes after 11.23 a.m., they continued to fluctuate abnormally for some time after. Then, in the early hours of September 2, approximately eighteen hours after the Carrington’s initial observation, the instruments at Kew reacted even more vigorously, as did recording devices at Greenwich, in Paris, throughout Europe, in India and many other parts of the globe.

The magnetic storm now assailing the earth, with the arrival of particles carried on the solar wind, played havoc with all manner of electrical devices throughout the world. Telegraphic equipment functioned erratically, if at all, with bells ringing at inappropriate times, overheating caused fires in telegram receivers, operators page 21 suffered electric shocks and overhead cables melted and fell from their poles. In some facilities instruments were hurriedly disconnected, to avoid irreparable damage. For a period telegraphic communications within and between nations all but ceased, with serious impacts on commerce, news and intelligence.

So what happened Down Under? While the majority of the 1859 reports were from the northern hemisphere, there was one confirmation from Australia that the Aurora Australis was also fired up. Was anything reported in New Zealand? By courtesy of Papers Past, commentaries have been found in five New Zealand newspapers: Daily Southern Cross Auckland; Lyttelton Times; Taranaki Herald New Plymouth; Nelson Examiner and the Colonist, Nelson.

Nelson’s Colonist newspaper was a little more effusive, reporting on August 30

No instances of dangerous, or even erratic, disturbances of telegraphic or other electrical facilities appear to have been reported in the New Zealand newspapers.

“Carrington’s flare”, as it is now known, can be flagged as a seminal event in the history of solar astronomy for two reasons, for the development of the science itself, and for the fact that, in the intervening 150 years, there has never been a repetition of a solar event of the magnitude he witnessed. Despite the ensuing interest by fellow astronomers and other scientists, the contiguity of the events he had observed and the dramatic experiences with all manner of magnetic and electrical equipment and infrastructure, science in the late 1850s had not yet contemplated the possible dependence of these earth-bound phenomena on violent solar activities.

A century and a half later these interactions are much better understood, as are the processes of nuclear fusion powering the sun, the mechanisms triggering sunspot formation and solar outbursts, the cyclical nature of sunspot activity, the nature of the radiation and particles released, and the means by which they traverse the void to earth. But such refinements were not gained without several decades of controversy, in which Carrington became an early protagonist, as did succeeding generations of astronomers and physicists. Nor were they gained without the development of increasingly sophisticated equipment for data collection and processing.

This may be an appropriate time to remind ourselves of the 1859 events, for applications of that sophisticated science to current studies of the sun are detecting increasingly vigorous levels of solar activity following a long period of relative quiescence, leading to predictions of another outburst of similar proportions. The global effects in the 21st century would paralyse almost every field of human endeavour in ways not even imagined in 1859.

References

• Clark, Stuart. (2007). The sun kings: The unexpected tragedy of Richard Carrington and the tale of how modern astronomy began. New Jersey: Princeton University Press.
• Vastag, Brian. (2011, June 26). Scientists Fear Solar “Coronary”. Sunday Star Times from Washington Post.
• Newspaper extracts courtesy of “Papers Past”, National Library of New Zealand: http://paperspast.natlib.govt.nz/cgi-bin/:
• Colonist, 1859, August 30.
• Daily South Cross, September 2, 9, 1859.
• Lyttelton Times, September 3, 1859.
• Nelson Examiner, August 31, September 7, 1859.
• Taranaki Herald, September 5, 1859.