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 Discovery of an Extragalactic Hot Molecular Core
29.09.2016 | National Astronomical Observatory of Japan

nachricht Swiss space research reaches for the sky
29.09.2016 | Schweizerischer Nationalfonds SNF

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: New welding process joins dissimilar sheets better

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of light metals.
Scientists at the University of Stuttgart have now developed two new process variants that will considerably expand the areas of application for friction stir welding.
Technologie-Lizenz-Büro (TLB) GmbH supports the University of Stuttgart in patenting and marketing its innovations.

Friction stir welding is a still-young and thus often unfamiliar pressure welding process for joining flat components and semi-finished components made of...

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

European Health Forum Gastein 2016 kicks off today

28.09.2016 | Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

 
Latest News

The first genome of a coral reef fish

29.09.2016 | Life Sciences

Gentle sensors for diagnosing brain disorders

29.09.2016 | Medical Engineering

Swiss space research reaches for the sky

29.09.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>