Auroral mystery solved: Sudden bursts caused by swirling charged particles

December 21, 2015
On the left is and aurora oval before the auroral breakup occursOn the right is a supercomputer simulation reveals how auroral breakups developHot charged particles, or plasmas, gather in near-Earth space -- just above the upper atmosphere of the polar region -- when magnetic field lines reconnect in space. This makes the plasma rotate, creating a sudden electrical current above the polar regions. Furthermore, an electric current overflows near the bright aurora in the upper atmosphere, making the plasma rotate and discharge the extra electricity. This gives rise to the 'surge', the very bright sparks of light that characterize substorms. Credit: Kyoto University

Auroras are dimly present throughout the night in polar regions, but sometimes these lights explode in brightness. Now Japanese scientists have unlocked the mystery behind this spectacle, known as auroral breakup.

For years, scientists have contemplated what triggers the formation of auroral substorms and the sudden bursts of brightness. Appearing in the Journal of Geophysical Research, the current study overthrows existing theories about the mechanism behind this phenomenon.

The Kyoto-Kyushu research team has revealed that hot charged particles, or plasmas, gather in near-Earth space—just above the upper atmosphere of the polar region—when magnetic field lines reconnect in space. This makes the plasma rotate, creating a sudden above the . Furthermore, an electric current overflows near the bright aurora in the , making the plasma rotate and discharge the extra electricity. This gives rise to the "surge", the very bright sparks of light that characterize substorms.

"This isn't like anything that us space physicists had in mind," said study author Yusuke Ebihara of Kyoto University.

Ebihara based the study on a supercomputer simulation program developed by Takashi Tanaka, professor emeritus at Kyushu University.

Auroras originate from plasma from the sun, known as the solar wind. In the 1970s, scientists discovered that when this plasma approaches the Earth together with magnetic fields, it triggers a change in the Earth's magnetic field lines on the dayside, and then on the night side. This information alone couldn't explain how the fluttering lights emerge in the sky, however.

The video will load shortly
A Japanese research team has solved how auroral breakups occur. Hot charged particles, or plasmas, gather in near-Earth space -- just above the upper atmosphere of the polar region -- when magnetic field lines reconnect in space. This makes the plasma rotate, creating a sudden electrical current above the polar regions. Furthermore, an electric current overflows near the bright aurora in the upper atmosphere, making the plasma rotate and discharge the extra electricity. This gives rise to the 'surge', the very bright sparks of light that characterize substorms. Credit: Yusuke Ebihara/Kyoto University

Scientists had come up with theories for separate parts of the process. Some suggested that acceleration of plasma from the reconnection of lines caused auroral breakup. Others argued that the electrical current running near the Earth diverts a part of the electrical current into the ionosphere for some unknown reason, triggering the bright bursts of light. This theory was widely accepted because it offered an explanation for why upward-flowing currents emerged out of our planet. But the pieces of the puzzle didn't quite fit well together.

Tanaka's supercomputer simulation program, on the other hand, offers a logical explanation from start to finish.

"Previous theories tried to explain individual mechanisms like the reconnection of the and the diversion of electrical currents, but there were contradictions when trying to explain the phenomena in its entirety," said Ebihara. "What we needed all along was to look at the bigger picture."

The current paper builds on earlier work by Ebihara and Tanaka about how the bursts emerge. This explores the succeeding processes, namely how the process expands into a large scale breakup.

The research also has the potential to alleviate hazardous problems associated with auroral breakups that can seriously disrupt satellites and power grids.

Explore further: Observing the onset of a magnetic substorm

More information: Y. Ebihara et al. Substorm simulation: Formation of westward traveling surge, Journal of Geophysical Research: Space Physics (2015). DOI: 10.1002/2015JA021697

Related Stories

Observing the onset of a magnetic substorm

September 2, 2014

Magnetic substorms, the disruptions in geomagnetic activity that cause brightening of aurora, may sometimes be driven by a different process than generally thought, a new study in the Journal of Geophysical Research: Space ...

What's it like to see auroras on other planets?

November 10, 2015

Witnessing an aurora first-hand is a truly awe-inspiring experience. The natural beauty of the northern or southern lights captures the public imagination unlike any other aspect of space weather. But auroras aren't unique ...

MMS mission delivers promising initial results

December 18, 2015

Just under four months into the science phase of the mission, NASA's Magnetospheric Multiscale, or MMS, is delivering promising early results on a process called magnetic reconnection—a kind of magnetic explosion that's ...

The solar wind breaks through the Earth's magnetic field

June 10, 2014

Space is not empty. A wind of charged particles blows outwards from the Sun, carrying a magnetic field with it. Sometimes this solar wind can break through the Earth's magnetic field. Researchers at the Swedish Institute ...

Recommended for you

Dark matter may be smoother than expected

December 7, 2016

Analysis of a giant new galaxy survey, made with ESO's VLT Survey Telescope in Chile, suggests that dark matter may be less dense and more smoothly distributed throughout space than previously thought. An international team ...

Cassini transmits first images from new orbit

December 7, 2016

NASA's Cassini spacecraft has sent to Earth its first views of Saturn's atmosphere since beginning the latest phase of its mission. The new images show scenes from high above Saturn's northern hemisphere, including the planet's ...

Saturn's bulging core implies moons younger than thought

December 7, 2016

Freshly harvested data from NASA's Cassini mission reveals that Saturn's bulging core and twisting gravitational forces offer clues to the ages of the planet's moons. Astronomers now believe that the ringed planet's moons ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.