Most people will be surprised to learn that our
planet orbits inside the Sun's outer atmosphere, known as the 'Heliosphere'.
Our planet circles the Sun inside a bubble of rarefied hydrogen and helium
that blows out from the Sun in the form of the 'Solar Wind', and this gas
extends out well beyond the orbit of Neptune, where it eventually collides
with the gas bubbles of nearby stars.
On Earth the word 'weather' refers to the
condition of the atmosphere. But there is weather in space too - determined by
the condition of the heliosphere. Disturbances in the heliosphere can cause
our planet to be bombarded by charged particles, and the magnetic storms that
result can disrupt radio communications, destroy satellites and endanger the
lives of astronomers. The intense gusts of the solar wind are prevented from
reaching our atmosphere by our planet’s magnetic field, a protection not
enjoyed on Venus or Mars.
In recent years, the planetary probes Pioneer 10
and 11, and Voyager 1 and 2 are reaching the edge of the heliosphere – the
region of our galaxy dominated by the Sun. 2007 is the International
Heliophysical Year, and scientists are only now coming to fully appreciate the
importance of the heliosphere to our planet’s well being. Spearheading this
effort is Dr Peter Gallagher, who has worked for with the Owens Valley Solar
Array and the Big Bear Solar Observatory (both in California) before going to
NASA to work with the SOHO and RHESSI space craft. Dr Gallagher is
currently a lecturer with the School of Physics in Trinity College
Dublin.
