Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Thin current sheets in space: where the action is

Much of the exciting action is space is confined to thin boundaries. The Universe is filled with plasma, a charged gas consisting of ions and electrons.
Thin sheets with currents separate large plasma regions in space. Scientists at the Swedish Institute of Space Physics (IRF) have now finally measured the fundamental properties of one of the waves mixing and accelerating plasmas within these sheets.

Around Earth, the processes accelerating electrons which hit the atmosphere and cause beautiful auroras are often initiated in thin current sheets. Similar processes, auroras and thin current sheets are found around other planets such as Jupiter and Saturn.
Plasma regions close to the hot solar surface are separated by thin current sheets, and similar boundaries should also be common around distant stars. In man-made plasmas, thin boundaries are found in the tokamak plasma employed in nuclear fusion research and space observations may help us understand fusion plasmas.

The solar wind blows plasma at the Earth’s magnetic field. This causes the so-called magnetotail, stretching several hundred thousand kilometres downstream from the Earth. There is a thin current sheet separating the northern and southern parts of the tail.

In large parts of space, the plasma is too tenuous for the particles to actually collide. However, since the particles are charged, electric fields caused by some particles will interact with other particles. Often rather specific waves in the electric field interchange energy between the plasma particles. These waves replace ordinary collisions.

The lower hybrid drift waves have been studied for 50 years and are thought to play an important role in these narrow current sheets. However, due to their relatively short wavelength, it has been impossible to observe their fundamental properties. IRF’s scientists have now, for the first time, been able to make direct measurements of the wavelength and velocity of these waves.

It has not been possible to measure the wavelength with a single spacecraft, but this can be done with the European Space Agency’s four Cluster spacecraft. Taking advantage of the short 40 km separation between two of the four spacecraft in the magnetotail during August 2007, the scientists could observe the same wave propagating past first one and then the other spacecraft. The wavelength could be determined to be about 60 km (comparable to the radius of the electron gyro-motion in the magnetic field) and the velocity to about 1000 km/s (comparable to the ion velocity). The results appeared in the scientific journal Physical Review Letters on 31 July.

"We see small vortices that propagate in this narrow current sheet. They are just big enough so that both of the spacecraft can see them at the same time and be sure it is the same structure," says Cecilia Norgren of the Swedish Institute of Space Physics and a PhD student at Uppsala University. "The assumptions, used for several decades, have finally been verified by direct observations."
Cecilia Norgren, PhD student, IRF and Uppsala University, tel. +46-18-471 5934,

Mats André, Professor, IRF, tel. +46-70-779 2072,

Rick McGregor, Information Officer, IRF, tel. +46-980-79178,

Rick McGregor | idw
Further information:

More articles from Physics and Astronomy:

nachricht Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1
21.03.2018 | Fraunhofer-Institut für Hochfrequenzphysik und Radartechnik FHR

nachricht Taming chaos: Calculating probability in complex systems
21.03.2018 | American Institute of Physics

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: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Custom sequences for polymers using visible light

22.03.2018 | Materials Sciences

Scientists develop tiny tooth-mounted sensors that can track what you eat

22.03.2018 | Health and Medicine

Mat baits, hooks and destroys pollutants in water

22.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>