Solar physicists 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.

CMEs are 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.

Dr. Lucie 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.’

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.

Until recently 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.

Dr. Green 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 hazardous, phenomena.’

Dr. Lucie Green (unavailable Friday afternoon)
Mullard Space Science Laboratory
UCL, Holmbury St. Mary
Tel: 01483 204257
Mobile: 0788 4426104
Fax: 01483 278312

Julia Maddock
PPARC Press Office
Tel: 01793 442094


Images are available from or from Julia Maddock in the PPARC
press office (contact details below). The images show false colour images of
coronal mass ejections as taken by the coronagraph LASCO onboard the
international SoHO satellite. They reveal that the gigantic ejections
contain twisted solar material and travel at speeds 1000’s of times that of

Credit: Images courtesy of SOHO/LASCO consortium. SOHO is a project of
international co-operation between ESA and NASA.

The Particle Physics and Astronomy Research Council (PPARC) is the
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