Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Unveiling the aurora

12.12.2001


The Northern Lights: powered by an immense electrical circuit.
© Corbis


Satellites have detected the shifting forces that weave the Northern Lights.

A group of four spacecraft has given scientists their first glimpse of the immense electrical circuit above the Earth that creates the shimmering veil of the aurora borealis, or Northern Lights1.

In January 2001 the four satellites of the European Space Agency’s Cluster mission encountered a beam of electrons moving away from the Earth near the North Pole. The beam was on the outward-bound leg of its journey from the Sun, through the Earth’s atmosphere - where it creates the aurora - and back into space.



Passing through the beam in close succession, the satellites recorded it growing and vanishing over 200 seconds, Goran Marklund of the Royal Institute of Technology in Stockholm, Sweden, and co-workers report. Such fluctuations leave their mark in the shifting curtains of the spectacular display over the North Pole.

Auroral displays happen when the solar wind - the stream of electrically charged particles ejected from the Sun - penetrates the ionosphere, the region of the Earth’s upper atmosphere between 80 and 200 km above the ground. The edge of the planet’s magnetic field deflects most of the solar wind. But the field lines channel some particles down towards the poles.

The particles collide with molecules in the atmosphere above the North Pole, producing the glow of the aurora borealis.

The particles streaming down from the Sun are mostly negatively charged electrons. The funnel-shaped electric field at the North Pole focuses these electrons into a kind of beam. This beam generates the aurora when it enters the ionosphere, which is rich in charged particles.

Beam up

But the electrons must keep moving. The beam gets bent sideways in the auroral region so that it runs parallel to the Earth’s surface, before turning upward and streaming back into space.

It has long been thought that another, positively charged electric field draws the electrons up from the ionosphere and fires them back into space. According to this idea, the aurora is a consequence of this vast electrical circuit, in which electrons flow from a negative to a positive terminal, like those of a battery.

The aurora owes its ever-changing beauty to the inconstancy of the circuit. Solar winds ’beat’ the magnetic fields, causing them to flicker on and off.

Cluster consists of four satellites launched in 2000 - Rumba, Salsa, Samba and Tango - that orbit between 19,000 and 119,000 kilometres above the Earth, passing in and out of the planet’s magnetic field.

Previous spacecraft have detected the upward flow of electrons. But it hasn’t been possible to follow how the beam changes over time. The Cluster mission can study this because the four satellites, orbiting in formation, pass through the same region of the magnetic field at different times.

The upward beam of electrons creates a kind of ’anti-aurora’ or black aurora, sometimes visible from the ground as black patches or rings in the Northern Lights.

References

  1. Marklund, G. T. et al. Temporal evolution of the electric field accelerating the electrons away from the auroral ionosphere. Nature, 414, 724 - 727, (2001).

PHILIP BALL | © Nature News Service

More articles from Physics and Astronomy:

nachricht Colloidal Quantum Dot Photodetectors can now see further than before
21.01.2020 | ICFO-The Institute of Photonic Sciences

nachricht Compact broadband acoustic absorber with coherently coupled weak resonances
21.01.2020 | Science China Press

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: A new look at 'strange metals'

For years, a new synthesis method has been developed at TU Wien (Vienna) to unlock the secrets of "strange metals". Now a breakthrough has been achieved. The results have been published in "Science".

Superconductors allow electrical current to flow without any resistance - but only below a certain critical temperature. Many materials have to be cooled down...

Im Focus: Programmable nests for cells

KIT researchers develop novel composites of DNA, silica particles, and carbon nanotubes -- Properties can be tailored to various applications

Using DNA, smallest silica particles, and carbon nanotubes, researchers of Karlsruhe Institute of Technology (KIT) developed novel programmable materials....

Im Focus: Miniature double glazing: Material developed which is heat-insulating and heat-conducting at the same time

Styrofoam or copper - both materials have very different properties with regard to their ability to conduct heat. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz and the University of Bayreuth have now jointly developed and characterized a novel, extremely thin and transparent material that has different thermal conduction properties depending on the direction. While it can conduct heat extremely well in one direction, it shows good thermal insulation in the other direction.

Thermal insulation and thermal conduction play a crucial role in our everyday lives - from computer processors, where it is important to dissipate heat as...

Im Focus: Fraunhofer IAF establishes an application laboratory for quantum sensors

In order to advance the transfer of research developments from the field of quantum sensor technology into industrial applications, an application laboratory is being established at Fraunhofer IAF. This will enable interested companies and especially regional SMEs and start-ups to evaluate the innovation potential of quantum sensors for their specific requirements. Both the state of Baden-Württemberg and the Fraunhofer-Gesellschaft are supporting the four-year project with one million euros each.

The application laboratory is being set up as part of the Fraunhofer lighthouse project »QMag«, short for quantum magnetometry. In this project, researchers...

Im Focus: How Cells Assemble Their Skeleton

Researchers study the formation of microtubules

Microtubules, filamentous structures within the cell, are required for many important processes, including cell division and intracellular transport. A...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

„Advanced Battery Power“- Conference, Contributions are welcome!

07.01.2020 | Event News

 
Latest News

A new look at 'strange metals'

21.01.2020 | Materials Sciences

Body's natural signal carriers can help melanoma spread

21.01.2020 | Health and Medicine

Structual color barcode micromotors for multiplex biosensing

21.01.2020 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>