"Every great advance in science has issued from a new audacity of
imagination"
~ John Dewey
Our current understanding of the aurora owes a
great deal of its knowledge to groundbreaking concepts proposed by pioneers
of auroral research.
Magnetic North Pole
If you have used a compass for navigation purposes, you know that the needle points to the north. However, it is not pointing to the geographic North Pole, it is pointing to the magnetic pole. The geographic and magnetic poles are not located at the same place. The location of the magnetic North Pole tends to shift over time. The center of the northern auroral oval is the magnetic North Pole, not the geographic North Pole.
The British Admiralty became interested in locating the magnetic pole
for navigation purposes in the nineteenth century. In the 1830s, Sir John
Ross, a scientist and polar explorer, and his cousin, James Ross, discovered
the northern magnetic pole on the west coast of Boothia Peninsula in Northern
Canada. Scientists track the movement of the geomagnetic pole which is
currently located near Ellesmere Island in Northern Canada.
The geomagnetic North pole
is currently located in
Northern Canada
click to see larger image
During the International Geophysical Year (1957-1958), auroral scientists found that the aurora is distributed along an oblong belt called the auroral oval. In 1970, images of the aurora obtained by satellites circling Earth confirmed the IGY discovery. Images revealed two beautiful rings of aurora, one in the northern hemisphere above the Arctic and the other in the southern hemisphere above the Antarctic continent. The northern oval is called the aurora borealis and the southern one, the aurora australis.
Auroral oval
click to see larger image
Magnetosphere
The concept of the magnetosphere was developed by
Sydney Chapman and his student Vincenzo Ferraro. It was originally referred
to as the Chapman-Ferraro cavity. The magnetosphere has a complicated
internal structure, consisting of the Van Allen belts, the plasma sheet,
and the magnetotail.
Sydney Chapman
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Van Allen belts
The Van Allen belts were discovered by University of Iowa professor James
Van Allen in the first triumph of the US space exploration program. These
radiation belts are bands of highly energized particles trapped in Earth's
geomagnetic fields. Auroral scientists have learned that the magnetized
planets, such as Jupiter and Saturn, have a magnetosphere and aurora,
while the non-magnetized planets, such as Venus and Mars, do not have
a magnetosphere or aurora.
James Van Allen
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Richard C. Carrington, an English solar physicist and astronomer, made the first tentative connection between solar activity and auroral displays. In 1859 he observed a solar flare which was followed by intense auroral activity the next night. The science world was deeply skeptical and this solar-terrestrial connection was still not widely accepted 50 years later despite exhaustive studies demonstrating the correlation between solar activity, auroral activity, and geomagnetic disturbances.
Sketch of sunspots
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Geophysical Institute
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