30 August 2002 - The Sun's twisted mysteries
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.'
Image 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.
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.'
Contacts
Dr. Lucie Green
Mullard Space Science Laboratory
UCL, Holmbury St. Mary
Dorking, Surrey RH5 6NT
Tel: 01483-204257
Fax: 01483-278312
Email: lmg@mssl.ucl.ac.uk
