Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Thin current sheets in space: where the action is

01.08.2012
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, cecilia.norgren@irfu.se

Mats André, Professor, IRF, tel. +46-70-779 2072, mats.andre@irfu.se

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

Rick McGregor | idw
Further information:
http://www.vr.se
http://www.cluster.irfu.se/

More articles from Physics and Astronomy:

nachricht When fluid flows almost as fast as light -- with quantum rotation
22.06.2018 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

nachricht Thermal Radiation from Tiny Particles
22.06.2018 | Universität Greifswald

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: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>