PhD student Erik Engwall of Uppsala University and the Swedish Institute of Space Physics led the study, which uses data from the European Cluster satellites and has just been published in Nature Geoscience.
The new observations show that the polar wind, a very dilute wind of hydrogen and oxygen, flows unimpeded to very high altitudes. The outflow has previously only been possible to study from satellites at low altitudes, so it was not clear if it actually continued far into space or if it spread out and soon returned to Earth. It is now clear that the particles are actually lost from Earth, as the Cluster measurements have followed them flow to an altitude of almost ten times the diameter of the Earth.
"The polar wind is no threat to the atmosphere", says study leader Erik Engwall, pointing out that an outflow of the magnitude observed will not make any dramatic change to our atmosphere even during the full expected lifetime of the solar system. But similar phenomena may be more important for other celestial bodies. "To understand how our atmosphere evolves is also important for understanding other atmospheres that can harbour life", adds Erik Engwall.
The discovery was made when the scientists tried to understand why the Cluster instrument provided by the Uppsala team seemed to give unrealistic results in space above the Earth's polar regions. "In regions of space where we expected to find very weak electric fields, we were surprised to find very strong fields in a direction that was just plain impossible", says Anders Eriksson, a scientist operating the Electric Fields and Waves instrument. By computer simulation, Erik Engwall could show that the unexpected results were due to the spacecraft encountering a supersonic wind of charged particles flowing away into space from the Earth's polar regions. The team could thus transform the apparent "measurement error" into a new method of observing the polar wind at unprecedented distances from the Earth. "In this region, the outflow was completely invisible to satellites until revealed by our new method", says Erik Engwall.
The paper "Earth's ionospheric outflow dominated by hidden cold plasma" by Erik Engwall, Anders Eriksson, Chris Cully, Mats André, Roy Torbert and Hans Vaith will appear in the January 2009 issue of Nature Geoscience, and was published online on 14 December. The results will also be presented at the fall meeting of the American Geophysical Union in San Francisco on Wednesday 17 December.
Cluster is a cornerstone project of the European Space Agency (ESA) and consists of four satellites, which have flown, in formation around the Earth since the summer of 2000. The Swedish Institute of Space Physics and the University of New Hampshire are responsible for two instruments measuring electric fields by very different methods on each of the satellites, and it was by comparing the two sets of results that the discovery was made. The Swedish group is financed by the Swedish National Space Board and the American group by NASA.
* Erik Engwall, PhD student, Department of Physics and Astronomy, Uppsala University, email@example.com, +46-70-765 9566.
* Anders Eriksson, scientist, Swedish Institute of Space Physics, firstname.lastname@example.org, +46-18-471 5945, +46-70-171 3029.
* Mats André, professor, Swedish Institute of Space Physics, email@example.com, +46-70-779 2072 (available at the AGU meeting in San Francisco).Weitere Informationen:
Rick McGregor | idw
Study offers new theoretical approach to describing non-equilibrium phase transitions
27.04.2017 | DOE/Argonne National Laboratory
SwRI-led team discovers lull in Mars' giant impact history
26.04.2017 | Southwest Research Institute
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
28.04.2017 | Event News
20.04.2017 | Event News
18.04.2017 | Event News
28.04.2017 | Medical Engineering
28.04.2017 | Earth Sciences
28.04.2017 | Life Sciences