Curtain falls over aurora borealis

The aurora borealis is caused not by solar flares but by gigantic portions of the corona flowing out of the Sun

Published: Friday 15 April 1994

FIRST the myth: the spectacular light dance -- the massive vibgyor curtain of northern and southern lights that shift every decade or so from their polar homes to produce vivid displays in the temperate skies -- is orchestrated by solar flares, which are streaks of fiery clouds flying away from the Sun.

The myth broken: the choreographers are actually large chunks of the corona -- the hot gaseous layer surrounding the Sun -- tearing themselves out of a violently agitated Sun.

The myth-breaker is Jack Gosling, an astrophysicist at the Los Alamos National Laboratory who launched a campaign last year to convince others of the innocence of solar flares. He contends that northern lights -- or the aurora borealis -- are born of ejected lumps of solar mass, which appear as gigantic bubbles looping off the Sun's circumference. The bubbles lift off into space, leaving behind only bright legs rooted to the Sun (Nature, Vol 367, No 6464).

It was earlier believed that solar particles released and driven by the solar flares create magnetic storms on earth which disrupt electrical power systems and are often fatal for satellites. But Gosling and other scientists say that both solar flares and the aurorae are side effects of coronal mass ejections.

They have shown that the strong magnetic fields created during the ejection of the coronal mass are to be castigated for the damage, or thanked profusely for the awesome light display. As these solar fields approach the magnetic field of the earth, both are destroyed, releasing a lot of energy. This energy paves the way for the solar particles to gatecrash into the earth's atmosphere and, together with local particles, give form to the aurorae.

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