Ring of fire: Indian Ocean to see solar eclipse

A few lucky people in the Indian Ocean will be treated to a rare event on Monday when an annular solar eclipse will transform the Sun into a dark disc with a blazing ring-shaped corona around its rim.

In solar eclipses, the Moon moves between the Sun and Earth, casting its shadow on the terrestrial surface.

In an annular eclipse, a tiny shift in distance that results from celestial mechanics means the Moon does not completely cover the Sun's face, as it does in a total eclipse.

Instead, for those directly under the alignment, the Moon covers most of the Sun's surface, and a ring-like crown of solar light blazes from the edge of the disk.

For those watching from the fringe of the track, the Sun is partially obscured, as if a bite has been taken out of it.

According to veteran NASA eclipse-watcher Fred Espenak, the total eclipse track will run from west to east on Monday from 0606 GMT to 0952 GMT.

It will traverse the Indian Ocean and western Indonesia before petering out just short of Mindanao, the Philippines.

The partial eclipse will be seen in a much wider swathe, including the southern third of Africa, Madagascar, Australia, Southeast India, Southeast Asia and Indonesia.

It will be the only annular solar eclipse this year. The last was on 7 February, 2007, and after Monday, the next one will be on 15 January, 2010.

The big event for eclipse junkies this year is on July 22, when a total solar eclipse will be visible from India and China, the world's two most populous countries.

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One can understand why long range radio propagation might be affected during a solar eclipse, because the ionizing radiation of the sun is temporarily intercepted by the moon. There is no such obvious explanation for radio propagation problems during lunar eclipses. Nevertheless, we have the following observation by L.M. Nash:

"During 1978/79, I was stationed on Diego Garcia (U.S. Naval base in the Indian Ocean). I was an amateur radio operator then, and one night there was a total (or near total) eclipse of the moon. I was in contact with a station in Utah, on the 15 meter (21.0 to 21.45 MHz) band. When the eclipse started, the Utah station faded out, and all I heard was a sizzling, crackling noise across the entire 15-meter band. This started and ceased within the duration of the eclipse. I then reestablished contact with the Utah station, who was still on the same frequency talking to a friend of his. When I asked him what happened, he stated that my signal had just disappeard."

(Nash, Lemuel M.; personal communication, May 12, 1990. From Science Frontiers #71, SEP-OCT 1990. )

Our thanks to Mike Terry for spotting this article