Scientists weather a space storm to find its origin

By taking front row seats during a celestial storm, a team led by UCL (University College London) scientists have studied a huge eruption from its birth on the Sun and when it reaches Earth.

Triggered by an explosion on the Sun which has 5,0000 million times more energy than the Hiroshima bomb, these blasts of gas, known as coronal mass ejections, can engulf the Earth.

The Earth's magnetic field, the magnetosphere, protects the planet from the full brunt of these blasts, but when the coronal mass ejection's fields collide directly with it they can excite geomagnetic storms. In extreme cases they cause electrical power outages and damage to communications satellites.

Reporting in the August 5th edition of the journal Geophysical Research Letters the team of researchers from the UK and France used SOHO , the four Cluster, and ACE spacecraft to identify the source of a coronal mass ejection and analyse how its magnetic field changes on its path to Earth.

The direct measurement confirms previous Earth-bound predictions and takes researchers a step closer to forecasting storms.

Dr Louise Harra, of UCL Mullard Space Science Laboratory, explains: "Previously, there's been much speculation about the shape of the magnetic field and how it might change on its journey from the Sun to Earth. Using complementary satellites we have been able to see that the magnetic field changes very little on its journey.

"If we are to successfully predict storms we need to be able to identify an Earth-directed coronal mass ejection as it leaves the Sun and work out how it evolves."

Coronal mass ejections are caused by loop-like magnetic field lines on the Sun's surface. They're in constant motion and when they bump into each other if their polarities are different it can cause ejections or flares.

Their frequency varies in an 11 year solar cycle and during solar maximum you can get up to 10 coronal mass ejections and flares a day. The next solar maximum is due in 2010 but it is during a solar minimum, which we are currently experiencing, when fewer flares occur but are often more dramatic such as the one analysed.

The coronal mass ejection was detected on 20 January 2004 by the SOHO and Cluster spacecraft and they were used to identify the sources of the ejection.

Two days later on its journey to Earth the ejecta magnetic field passed the four Cluster spacecraft and the tetrahedral conformation allowed sampling of the speed and direction of the field. Similar calculations were carried out by ACE in an orbit around the polar region.

"SOHO and Cluster spacecraft are ideally suited to working together - SOHO 'sees' the explosions from the Sun and Cluster 'feels' them. Our next step is to predict the eruption of storms on the Sun, which we hope to achieve next summer when the Solar-B mission is launched," says Dr Harra.

For further information, please contact:

Dr Louise Harra, UCL Mullard Space Laboratory, Tel: +44 (0) 1483 204141, Email: lkh@mssl.ucl.ac.uk

Judith H Moore, UCL Media Relations, Tel: +44 (0) 20 7679 7678 (int: 07678), Mobile: +44 (0)77333 075 96, Email: Judith.moore@ucl.ac.uk

Notes to editors

Journal: Geophysical Research Letters (05/08/05)

Title: 'Relating near-Earth observations of an interplanetary coronal mass ejection to the conditions at its site of origin in the solar system'

Authors: A Fazakerley (1), L.K Harra (1), J. L Culhane (1), L. van Driel-Gesztelyi (1, 2, 3), E. Lucek (4), S.A. Matthews (1), C.J. Owen (1), C. Mazelle (5), A Balogh (4) and R. Reme (5)

(1) Mullard Space Science Laboratory, University College London, Dorking, UK

(2) Also at, Konkoly Observatory, Hungarian Academy of Sciences, Budapest, Hungary

(3) Also at, Observatorie de Paris, Meudon, France

(4) Space and Atmospheric Physics, Imperial College London, South Kensington, UK

(5) Centre d'Etude Spatiale des Rayonnements, Toulouse, France

About UCL Mullard Space Science Laboratory (MSSL)

MSSL is the Space and Climate Physics Department of UCL and is situated in rural Surrey. The department moved from London to its present location in Holmbury House after it was purchased with funds donated by the Mullard electronics company. 150 scientists work at MSSL across several areas; solar and stellar physics, planetary and plasma physics, astrophysics, detector physics and climate physics. The laboratory houses world-class facilities to design, build and test instrumentation as well as to analyse the data taken by the instruments in space.