August 2002 - The Sun's twisted mysteries
at the Mullard Space Science Laboratory (MSSL, University College London)
in Surrey have found new clues to the thirty year old puzzle of why the Sun
ejects huge bubbles of electrified gas, laced with magnetic field, known
as coronal mass ejections (CMEs). In a paper published this month in the
Journal of Solar Physics, they explain that the key to understanding CMEs,
which can cause electricity black outs on Earth, may be due to twisted magnetic
fields originating deep within the heart of the Sun.
violent solar eruptions which travel at 1000 times the speed of Concorde
and contain more mass then Mt. Everest. They have proved hazardous to
modern technology, seen most dramatically in 1989 when a CME magnified
the solar wind, which then slammed into the Earth. This caused widespread
blackouts, which cost the Canadian national grid several million of pounds
in damage to their systems. On the more aesthetic side, CMEs are also
responsible for the northern (and southern) lights, Aurora Borealis.
Green of MSSL says, 'Ultimately we need to know why CMEs occur so that
one day we will be able to predict them just like we do with the weather
on Earth. This is the new science of Space Weather.'
courtesy of SOHO/LASCO consortium.
CMEs are seen
when the Sun is artificially eclipsed and they contain beautifully twisted
structures. Tracing them back to their solar origin reveals very twisted
structures on the surface of the Sun too. This twist is contained in the
Sun's magnetic field and, just like a stretched elastic band, it contains
energy, which then blasts the CME into space.
the source of the twist (which is known more precisely as helicity) has not
been known. There are two options, the first being that it is created at
the surface of the Sun. Now however, a group of scientists at MSSL, with
colleagues in France and Argentina, have studied CME source regions using
data from the international SoHO and Yohkoh satellites, and found that the
second, more likely explanation, is that the magnetic field becomes charged
with helicity, or twist, deep within the Sun. Here, the gas is constantly
rising and falling due to the heat created by the fusion furnace at the Sun's
core. Indeed, it may even be related to the creation of the magnetic field
itself, known as the solar dynamo.
says, 'We have only known about CMEs for the last 30 years. The UK plays
a leading role in solar physics and these new results are helping us make
substantial advancements in our understanding of these beautiful, but potentially
Mullard Space Science Laboratory
UCL, Holmbury St. Mary
Dorking, Surrey RH5 6NT