ESA title
Cluster and Double Star orbits on 8 May 2004
Science & Exploration

Details of solar particles penetrating the Earth’s environment revealed

03/10/2006 3855 views 2 likes
ESA / Science & Exploration / Space Science / Cluster

Co-ordinated efforts by China/ESA’s Double Star and ESA’s Cluster spacecraft have allowed scientists to zero in on an area where energetic particles from the Sun are blasting their way through the Earth’s magnetic shield. Solar material penetrating the Earth's magnetic shield can represent a hazard to both astronauts and satellites.

On 8 May 2004, one of the two Double Star satellites (TC-1) and all four Cluster spacecraft found themselves in the firing line. For about 6 hours, the Cluster spacecraft were buffeted every 8 minutes by intense flows of electrically charged particles released by the Sun. The Double Star TC-1 spacecraft had it even rougher, being blasted every four minutes for eight hours.

During such events, magnetic channels created by the merging of the Sun and the Earth’s magnetic fields allow solar particles to break through the Earth’s magnetic shield and penetrate the Earth’s environment. Physicists call the occurrence of these magnetic channels Flux Transfer Events. Each magnetic channel appears like a curve shaped tube that can be anything from 5000 to 25000 kilometres in diameter. One end of the magnetic flux tube is connected to Earth while the other end is connected to the solar wind.

The basic physical mechanism responsible for the occurrence of flux transfer events is called magnetic reconnection. In the 1950s, space physicists believed that magnetic reconnection let solar particles break through at a steady rate. That view changed in the late 1970s, when several studies showed that the magnetic reconnection could also be intermittent and take place in pulses, lasting a few minutes. Each pulse produces a magnetic flux tube (a Flux Transfer Event).

Simulation of a portion of Earth’s magnetic field on 8 May 2004
Simulation of a portion of Earth’s magnetic field on 8 May 2004

On 8 May 2004, these magnetic flux tubes swept over Cluster and Double Star again and again. As the Cluster and Double Star data clearly showed, the same location underwent magnetic reconnection several times, creating new successive magnetic flux tubes to channel more charged particles towards the Earth. The observations stopped probably because the spacecraft moved out of range and not because the reconnection region weakened in any way.

The data from the five spacecraft allowed scientists led by Aurélie Marchaudon of the Laboratoire de Physique et Chimie de l’Environnement, Centre Nationale de la Recherche Scientifique (CNRS) and Université d’Orléans, Orléans, France to triangulate the location of the magnetic reconnection region, and to deduce its size. They found that the reconnection site was located on the daylight west side of the Earth’s magnetic shield and was around 25000 kilometres across. A computer simulation of the event, conducted by Jean Berchem of the University of California Los Angeles (UCLA) and his team, confirmed the possibility of magnetic reconnection occurring at that location.

Although intermittent reconnection has been observed in the past, this was one of the longest series of continuous observations ever taken of a magnetic reconnection region in the Earth’s magnetosphere. Perhaps most surprising is that 8 May 2004 was just relatively a normal day for the Earth’s magnetic field. There were no large magnetic storms on Earth, or spectacular aurorae to fill the night sky. However, Cluster and Double Star revealed that energetic particles from the Sun were blasting their way through the Earth’s magnetic shield and penetrating the Earth’s environment.

Each day, Cluster and Double Star return more observations that allow scientist to understand the invisible magnetic turbulence high above our heads.

Notes to Editors

More information on these findings can be found in the paper “Simultaneous Double Star and Cluster FTEs observations on the dawnside flank of the magnetosphere” (Ann. Geophys., 23, 2877-2887, 2005), by A.Marchaudon, C. J. Owen, J.-M. Bosqued, R.C. Fear, A.N. Fazakerley, M.W. Dunlop, A. D. Lahiff, C. Carr, A. Balogh, P.-A. Lindqvist and H. Rème, and in the paper “Using DOUBLE STAR and CLUSTER synoptic observations to test global MHD simulations of the large-scale topology of the dayside merging region” (Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract SM23-06, 2005), by J.Berchem, A. Marchaudon, J. M. Bosqued, C. P. Escoubet, M. Dunlop, C. J. Owen, H. Reme, A. Balogh, C. Carr, A. N. Fazakerley, and J. Cao.

For more information

Aurélie Marchaudon, CNRS and Université d’Orléans, France
Email: aurelie.marchaudon @ cnrs-orleans.fr

Jean Berchem, University of California Los Angeles (UCLA)
Email: jberchem @ ucla.edu

Philippe Escoubet, ESA Cluster and Double Star Project Scientist
Email: philippe.escoubet @ esa.int

Related Links

Science & Exploration

Cluster factsheet

2763 views 0 likes
Read
Cluster 2, Artist's view
Enabling & Support

Cluster muscles back from deep hibernation

06/10/2006 1198 views 2 likes
Read
Aurorae over Canada
Science & Exploration

ESA’s Cluster mission establishes why Earth’s aurorae shine

24/08/2006 1348 views 0 likes
Read
Earth's magnetosphere- an artist's impression
Science & Exploration

Cluster makes an effervescent discovery

20/06/2006 1496 views 2 likes
Read
Sketch of the Earth magnetosphere
Science & Exploration

ESA’s Cluster flies through Earth’s electrical switch

19/05/2006 2551 views 0 likes
Read
Artist's impression of  ESA's  Cluster spacecraft
Science & Exploration

Cluster helps to protect astronauts and satellites against …

22/12/2005 1951 views 1 likes
Read
Artist's impression of positions of  Cluster, Wind and ACE spacecraft
Science & Exploration

Satellites see largest jet of particles created between Sun…

11/01/2006 1274 views 0 likes
Read
Artist's impression of  ESA's  Cluster spacecraft
Science & Exploration

Cluster helps to protect astronauts and satellites against …

22/12/2005 1951 views 1 likes
Read
Micro turbulence seen by Cluster
Science & Exploration

From ‘macro’ to ‘micro’ – turbulence seen by Cluster

10/08/2005 2860 views 1 likes
Read
The magnetosphere - a natural protective bubble
Science & Exploration

Cluster's new view of near-Earth space

16/02/2001 1975 views 1 likes
Read
Sun-Earth day events
Science & Exploration

How the Sun affects us on Earth

26/06/2003 36405 views 221 likes
Read
Aurora borealis
Science & Exploration

Space weather

6483 views 27 likes
Read
Science & Exploration

What are solar flares?

176487 views 708 likes
Read