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Science Frontiers ONLINE No. 119: Sep-Oct 1998 |
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Auroral Maps!
Auroral arcs are created by electrical currents flowing high in the ionosphere -- usually higher than 100 kilometers according to current [!] thinking. Therefore, scientists do not really expect to see terrestrial topography reflected in auroral geometry. Nevertheless, T. Pulkkinen of the Finnish Meterological Institute reported to the May 1998 meeting of the American Geophysical Union that coastlines somehow coax auroral arcs to align with them. In some 200 hours of observation along the Norwegian coast, there were nine clear-cut cases where auroral arcs lined up northsouth directly above the coastline. These alignments lasted 5-10 minutes.
L. Frank (of icy-comet notoriety) confirmed this effect with observations from NASA's Polar satellite. Sometimes auroral arcs aligned themselves parallel to the Greenland coast for hundreds of kilometers. Auroral arcs that fanned out east-to-west seemed to hit a barrier when they reached the Greenland coastline; they seemed to be deflected by it, even though the coast was more than 100 kilometers beneath them.
(Hecht, Jeff; "Leading Lights," New Scientist, p. 16, May 30, 1998.)