Press release: Swedish Institute of Space Physics, Kiruna, 2004-11-11

Roller-coaster in space!

"Mirror modes" revealed by Cluster scientists!

For over 35 years scientists were puzzled by observations of large-amplitude pulsations of the magnetic field between the bow shock and the magnetopause. The magnetic pulses represent increases of the magnetic field strength by a factor of 2 to 3 or decreases by 50-90 % over a distance of 1000 km. These structures can be compared to a gigantic roller-coaster on which all particles from the solar wind must ride before they can approach the Earth's magnetic field. They were named "mirror modes" some 30 years ago, but no explanatory physical model existed until a recent breakthrough made at IRF-Uppsala with use of Cluster measurements.

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In a recent article published in Geophysical Research Letters scientists from the Swedish Institute of Space Physics in Uppsala were able to explain and reproduce with a theoretical model the observed properties of these structures. The theory describes the magnetic structures as trains of magnetosonic solitons.

Such solitons are very common in space, and are expected to affect energy transfer from the solar wind into the magnetosphere. A model of such strongly nonlinear structures may be applied in astrophysical/cosmological theories, where direct in situ measurements are not possible.

The article is available online from the American Geophysical Union: http://www.agu.org/pubs/crossref/2004/2004GL021282.shtml

More information:

Kristof Stasiewicz, IRF Uppsala, tel. +46-18-471 5943, k.stasiewicz@irfu.se

Author's homepage: http://cluster.irfu.se/ks/

Rick McGregor, Information Officer, IRF, tel. +46-980-79178, rick.mcgregor@irf.se

Other web pages:

Swedish Institute of Space Physics (IRF): http://www.irf.se

Cluster Electric Field and Wave Experiment: http://www.cluster.irfu.se/

Cluster mission (ESA): http://clusterlaunch.esa.int/