Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cluster Mission Indicates Turbulent Eddies May Warm the Solar Wind

09.01.2013
The sun ejects a continuous flow of electrically charged particles and magnetic fields in the form of the solar wind -- and this wind is hotter than it should be. A new study of data obtained by European Space Agency's Cluster spacecraft may help explain the mystery.

The solar wind is made of an electrically-charged gas called plasma. One theory about the wind's puzzling high temperatures is that irregularities in the flow of charged particles and magnetic fields in the plasma create turbulence, which, in turn, dissipates and adds heat to its surroundings.


A 2-dimensional vision of the solar wind turbulence at the smallest scale seen yet, thanks to observations by Cluster satellites. The approximate location of the measurements is indicated on a graphic illustrating features of Earth’s magnetic environment. The inset shows conditions as would be seen facing the solar wind, with current sheets forming at the border of turbulent eddies. The trajectory of the Cluster spacecraft is marked on the inset by the black line and the color gradients represent the magnetic field strength intensity.
Background graphic: ESA/ATG Medialab
Inset: NASA/J. Dorelli

Using two separate sets of data sent back by Cluster, an international team of scientists has probed the spatial characteristics of this turbulence in more detail and at smaller scales than ever before. They saw evidence that the turbulence evolved to form very small “current sheets” -- thin sheets of electrical current that separate regions of rotated magnetic field.

“For the first time, we were able to obtain direct evidence for the existence of current sheets at these very small scales, where dissipation of magnetic energy into heat is thought to occur,” said Melvyn Goldstein, project scientist for Cluster at NASA’s Goddard Space Flight Center in Greenbelt, Md. Goldstein is a co-author of a paper on these results that appeared in the Nov. 9, 2012, issue of Physical Review Letters.

This solar wind is a non-stop gale of plasma, mainly protons and electrons, which originates in the sun’s searingly hot lower atmosphere. It blasts outward in all directions at an average speed of about 250 miles per second. The outflow is so energetic that it pulls along the sun’s magnetic field. The solar wind travels across the entire solar system, until it reaches the boundary with interstellar space. The plasma cools as it expands during its outward journey. However, the amount of cooling is much less than would be expected in a constant, smooth flow of solar particles since the density is so low that the particles cannot be receiving extra heat from the most common method on Earth: collisions.

By providing the first observations of these small current sheets, the Cluster data help confirm that such sheets may play an important role in the dissipation of the turbulence – meaning that as the turbulence cascades from larger disturbances to smaller ones, energy is taken out of the magnetic field and added to its surroundings as heat. The current sheets are more or less two-dimensional. They may are also be sites where the magnetic field lines reconnect and break, resulting in a transfer of energy to both particle heating and particle flows. Such magnetic reconnection occurs in many regions in the universe including in the solar wind, inside the sun and other stars, and in Earth’s magnetic environment, the magnetosphere. Finding direct evidence for magnetic reconnection at these scales is difficult with the present instrumentation, however, and resolution of that question may have to await the launch of NASA’s Magnetospheric Multiscale (MMS) mission in 2014, a mission that will focus on reconnection in the magnetosphere.

The team’s study made use of the high time resolution of the Spatio Temporal Analysis Field Fluctuation (STAFF) magnetometer, which is carried on each of the four Cluster spacecraft. STAFF is capable of detecting rapid variations in magnetic fields, which means that very small spatial structures can be recognized within the plasma.

The scientists examined two sets of STAFF observations. The first data were obtained on Jan. 10, 2004, when two Cluster spacecraft (C2 and C4) were separated along the solar wind flow direction by only 12 miles apart, while the two other spacecraft were much further away. At that time, STAFF was operating in rapid burst mode, during which it recorded 450 measurements of the magnetic field per second. Additional data were obtained by a single spacecraft (Cluster 2) on March 19, 2006.

"During the 2004 observation, both spacecraft were so close that they observed almost simultaneously the same structure in the solar wind as it passed them by. The magnetic field data showed the typical signature of a current sheet crossing," says Silvia Perri of the Università della Calabria, Italy, who is the lead author of the paper. At that time, the solar wind was flowing at about 350 miles per second. The current sheet event lasted only 0.07 seconds for both satellites and this corresponds to a spatial size of about 25 miles.

“This shows for the first time that the solar wind plasma is extremely structured at these very small scales,” says Perri. “It is clear that we are seeing a release of energy approaching smaller and smaller scales, which may contribute to the overall heating of the solar wind.”

For more information about NASA's MMS Mission, visit:
http://mms.gsfc.nasa.gov/
ESA and Karen C. Fox
NASA Goddard Space Flight Center, Greenbelt, MD

Karen C. Fox | EurekAlert!
Further information:
http://mms.gsfc.nasa.gov/
http://www.nasa.gov

More articles from Physics and Astronomy:

nachricht Nanostructures taste the rainbow
29.06.2017 | California Institute of Technology

nachricht X-ray photoelectron spectroscopy under real ambient pressure conditions
28.06.2017 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making Waves

Computer scientists use wave packet theory to develop realistic, detailed water wave simulations in real time. Their results will be presented at this year’s SIGGRAPH conference.

Think about the last time you were at a lake, river, or the ocean. Remember the ripples of the water, the waves crashing against the rocks, the wake following...

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Nanostructures taste the rainbow

29.06.2017 | Physics and Astronomy

New technique unveils 'matrix' inside tissues and tumors

29.06.2017 | Life Sciences

Cystic fibrosis alters the structure of mucus in airways

29.06.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>