Andrew Yee[_1_]
March 12th 08, 05:50 AM
ESA News
http://www.esa.int
7 March 2008
Solitary waves in translation
Swooping through space are solitary waves, which in theory do not change
form or lose energy as they go along. These waves, which exist on Earth in
different media, have been detected and explained for the first time in
space thanks to Cluster data.
In theory, these solitary waves, called solitons, propagate endlessly
maintaining their shape and form as well as velocity, which means that they
do not lose energy with time.
The phenomenon was first noticed in a water canal in England in 1834 by John
Scott Russel, who named it a 'wave of translation'. In water, solitons can
be created when a sudden impulse hits the medium and propagates along it.
This is made possible by a delicate balance of physical parameters that
reinforces the wave without additional energy input externally. Today, optic
fibres carry large amounts of information over very long distances making
use of soliton waves. This provides crystal-clear international phone calls
and fast internet connections.
On 30 March 2002, at a distance of 50 000 km from Earth, the satellites of
the Cluster constellation detected turbulence in the magnetopause, the outer
boundary of the magnetosphere. Simultaneous measurements by three of the
satellites detected a soliton breaking away from the turbulent region
towards the magnetosphere. The wave travelled for a long distance and
vanished at some point.
"Knowing the positions and separation of the spacecraft at that time, we
have found that the wave was 6-7 km in size and moved in towards the
magnetosphere at roughly 8 to 9 km/s. We couldn't have done this without
multiple spacecraft," said Raoul Trines of the Rutherford Appleton
Laboratory, UK, lead author of the study.
This phenomenon is very difficult to study on Earth because the soliton-like
structures that are observed tend to be much smaller in size, similar to the
size of the instruments that are used to probe them. Thus, the instruments
can disturb the phenomenon itself. Given the fact that the soliton detected
in space was very large, the disturbance caused to the wave as the
satellites probed it was negligible.
The observations performed by the Cluster satellites were found to be in
good agreement with computer simulations, confirming earlier theoretical
predictions of their existence.
"Thanks to its multiple spacecraft, Cluster has the unique capability to
differentiate spatial variations from temporal variations. This makes it the
first mission to confirm the theoretical prediction of solitons in space,"
said Philippe Escoubet, ESA's Cluster and Double Star Project Scientist.
"This result is truly one of the mission's scientific highlights," he added.
Notes for editors:
This article is based on the paper 'Spontaneous Generation of Self-Organized
Solitary Wave Structures at Earth's Magnetopause' by R. Trines, R. Bingham,
M. Dunlop, A. Vaivads, J. Davies, J. Mendonca, L. Silva, and P. Shukla,
published on 16 November 2007 in the Physical Review Letters.
For more information:
Dr Raoul Trines, Rutherford Appleton Laboratory, United Kingdom
Email: R.M.G.Trines @ rl.ac.uk
Philippe Escoubet, ESA Cluster and Double Star Project Scientist
Email: Philippe.Escoubet @ esa.int
Arnaud Masson, ESA Cluster Scientist
Email: Arnaud.Masson @ esa.int
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaSC/SEMKEPK26DF_index_1.html ]
http://www.esa.int
7 March 2008
Solitary waves in translation
Swooping through space are solitary waves, which in theory do not change
form or lose energy as they go along. These waves, which exist on Earth in
different media, have been detected and explained for the first time in
space thanks to Cluster data.
In theory, these solitary waves, called solitons, propagate endlessly
maintaining their shape and form as well as velocity, which means that they
do not lose energy with time.
The phenomenon was first noticed in a water canal in England in 1834 by John
Scott Russel, who named it a 'wave of translation'. In water, solitons can
be created when a sudden impulse hits the medium and propagates along it.
This is made possible by a delicate balance of physical parameters that
reinforces the wave without additional energy input externally. Today, optic
fibres carry large amounts of information over very long distances making
use of soliton waves. This provides crystal-clear international phone calls
and fast internet connections.
On 30 March 2002, at a distance of 50 000 km from Earth, the satellites of
the Cluster constellation detected turbulence in the magnetopause, the outer
boundary of the magnetosphere. Simultaneous measurements by three of the
satellites detected a soliton breaking away from the turbulent region
towards the magnetosphere. The wave travelled for a long distance and
vanished at some point.
"Knowing the positions and separation of the spacecraft at that time, we
have found that the wave was 6-7 km in size and moved in towards the
magnetosphere at roughly 8 to 9 km/s. We couldn't have done this without
multiple spacecraft," said Raoul Trines of the Rutherford Appleton
Laboratory, UK, lead author of the study.
This phenomenon is very difficult to study on Earth because the soliton-like
structures that are observed tend to be much smaller in size, similar to the
size of the instruments that are used to probe them. Thus, the instruments
can disturb the phenomenon itself. Given the fact that the soliton detected
in space was very large, the disturbance caused to the wave as the
satellites probed it was negligible.
The observations performed by the Cluster satellites were found to be in
good agreement with computer simulations, confirming earlier theoretical
predictions of their existence.
"Thanks to its multiple spacecraft, Cluster has the unique capability to
differentiate spatial variations from temporal variations. This makes it the
first mission to confirm the theoretical prediction of solitons in space,"
said Philippe Escoubet, ESA's Cluster and Double Star Project Scientist.
"This result is truly one of the mission's scientific highlights," he added.
Notes for editors:
This article is based on the paper 'Spontaneous Generation of Self-Organized
Solitary Wave Structures at Earth's Magnetopause' by R. Trines, R. Bingham,
M. Dunlop, A. Vaivads, J. Davies, J. Mendonca, L. Silva, and P. Shukla,
published on 16 November 2007 in the Physical Review Letters.
For more information:
Dr Raoul Trines, Rutherford Appleton Laboratory, United Kingdom
Email: R.M.G.Trines @ rl.ac.uk
Philippe Escoubet, ESA Cluster and Double Star Project Scientist
Email: Philippe.Escoubet @ esa.int
Arnaud Masson, ESA Cluster Scientist
Email: Arnaud.Masson @ esa.int
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaSC/SEMKEPK26DF_index_1.html ]