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Bursts of solar energy that periodically crash into the Earth’s atmosphere,
causing the aurora borealis or ‘northern lights’, may also be damaging the
ozone layer, according to NASA scientists. This image of solar electrons
hitting the upper atmosphere in a ring round the northern hemi-sphere was
taken by NASA’s Solar Anomalous and Magnetospheric Explorer satellite
(SAMPEX), which was launched last July. There is ‘growing evidence’, says
Linwood Callis of NASA’s Langley Research Center, that the electrons
‘trigger chemical reactions which may significantly influence global ozone
levels’. The electrons appear in bursts, most often when the sunspots are
at their minimum.

As they hit the atmosphere, the incoming electrons generate nitrogen oxides,
which can destroy ozone in the stratosphere. This could mean that ozone
destruction is related to the Sun’s 11-year sunspot cycles. But the story is
complicated by the fact that the same nitrogen compounds reduce the
destructive effect of chlorine in man-made CFCs and other compounds. The
SAMPEX satellite aims to investigate these reactions.

But in Britain, Joe Farman of the British Antarctic Survey, who discovered
the ozone hole over Antarctica a decade ago, said this week: ‘I thought we’d
killed this idea. It is a very local effect in the very upper atmosphere at
about 80 kilometres. Most of us think it is unlikely to have much of an
effect on the ozone layer, though of course it is dangerous to be too
certain.