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 First results of NSTX-U research operations
26.10.2016 | DOE/Princeton Plasma Physics Laboratory

nachricht Scientists discover particles similar to Majorana fermions
25.10.2016 | Chinese Academy of Sciences Headquarters

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: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Greater Range and Longer Lifetime

26.10.2016 | Power and Electrical Engineering

VDI presents International Bionic Award of the Schauenburg Foundation

26.10.2016 | Awards Funding

3-D-printed magnets

26.10.2016 | Power and Electrical Engineering

More VideoLinks >>>