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150th Anniversary of the Great Solar Storm

September 1st marks the one hundred and fiftieth anniversary of the great solar storm of 1859, which started with the flares on the Sun observed by R.C. Carrington and R. Hodgson. Around local noon that day, Carrington, an English amateur astronomer, made the rare observation of two intensely bright arcs seemingly igniting above the members of a large sunspot group. The brilliant arcs were short-lived, lasting only a few minutes before they subsided.

The sunspot group had appeared on August 26th, 1859 and the effects of the associated solar activity were widespread on Earth. For example, magnificent displays of the northern lights were seen as far south as the Carribean and Venezuela between August 28 and September 4. In the meteorological register of the Armagh Observatory, the aurorae were recorded as being bright and powerful on five of the nights. The New York Times for September 3rd, 1859 reported that ordinary print could be read by the light from the display at 1:00 a.m. The importance of these events is that sometimes solar flares can cause surges in electric currents generated on Earth. For example in 1859 such current surges were used to power communications by telegraph wire, and so, messages could still be transmitted from Boston to Portland even after all the batteries had been disconnected.

The 1859 solar storm confirmed the connection between the northern lights and the forces of electricity and magnetism, as the needles of some magnetometers, used to measure the Earth's magnetic field, flew off-scale. The white-light eruptions from the Sun's surface that September 1st are believed to have been the first-ever recorded solar flares. In addition, X-rays and ultraviolet radiation emanating from the Sun can disturb the ionosphere and so affect radio transmission, and heating of the Earth's atmosphere can also affect the drag on spacecraft. An intense solar storm can create currents on Earth that may sometimes overload the national power grids, as happened on 13th March 1989 when six million people lost power in the Quebec region of Canada. Quebec was paralysed for nine hours whilst engineers worked on a solution to the problem.

Recent research suggests that many of these powerful solar-terrestrial interactions can be traced to an ejection of material called a Coronal Mass Ejection. Such events are sometimes, but not always, associated with flares and are massive ejections of high-speed electrically-charged particles passing through the solar corona (the Sun's outer atmosphere) out into interplanetary space. This ejection of material carries a magnetic field as it travels through space and this could have initiated the effects seen on Earth in 1859.

This solar anniversary and the ensuing geomagnetic storm was important in many respects. It was the first flare ever recorded and it suggested to scientists for the first time that there was a link between the Sun, auroral activity and magnetism recorded on Earth. It stimulated renewed interest in the Sun and its relationship with the Earth and showed the importance of monitoring the variations in solar activity that have been recorded by humankind for hundreds of years.

FOR FURTHER INFORMATION PLEASE CONTACT: Srividya Subramanian at the Armagh Observatory, College Hill, Armagh, BT61 9DG. Tel.: 028-3752-2928; FAX: 028-3752-7174; sriat signarm.ac.uk

See also: Report by Margery Infield - PDF format

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Last Revised: 2009 August 24th
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