Behind the Power and Beauty of Northern Lights

by Nancy Atkinson on July 28, 2008

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Northern Lights.  Credit:  NASA

Northern Lights. Credit: NASA


The Aurora Borealis or Northern Lights are stunningly beautiful. But they can also disrupt radio communications and GPS signals, and even cause power outages. What’s behind the ethereal Northern Lights that causes them to shimmer and dance with colorful lights while sometimes wreaking havoc with electrical systems here on Earth? Using a fleet of five satellites, NASA researchers have discovered that explosions of magnetic energy a third of the way to the moon power substorms that cause sudden brightenings and rapid movements of the aurora borealis, called the Northern Lights. “We discovered what makes the Northern Lights dance,” said Dr. Vassilis Angelopoulos of the University of California, Los Angeles. Angelopoulos is the principal investigator for the Time History of Events and Macroscale Interactions during Substorms mission, or THEMIS.

The cause of the shimmering in Northern Lights is magnetic reconnection, a common process that occurs throughout the universe when stressed magnetic field lines suddenly snap to a new shape, like a rubber band that’s been stretched too far.

“As they capture and store energy from the solar wind, the Earth’s magnetic field lines stretch far out into space. Magnetic reconnection releases the energy stored within these stretched magnetic field lines, flinging charged particles back toward the Earth’s atmosphere,” said David Sibeck, THEMIS project scientist at NASA’s Goddard Space Flight Center. “They create halos of shimmering aurora circling the northern and southern poles.”

An explosion of energy increases in the brightness and movement of Northern Lights. Credit: NASA/Goddard Space Flight Center

An explosion of energy increases in the brightness and movement of Northern Lights. Credit: NASA/Goddard Space Flight Center


The data was gathered by five strategically positioned Themis satellites, combined with information from 20 ground-based observatories located throughout Canada and Alaska. Launched in February 2007, the five identical satellites line up once every four days along the equator and take observations synchronized with the ground observatories. Each ground station uses a magnetometer and a camera pointed upward to determine where and when an auroral substorm will begin. Instruments measure the auroral light from particles flowing along Earth’s magnetic field and the electrical currents these particles generate.

See animation of magnetic reconnection.

During each alignment, the satellites capture data that allow scientists to precisely pinpoint where, when, and how substorms measured on the ground develop in space. On Feb. 26, 2008, during one such THEMIS lineup, the satellites observed an isolated substorm begin in space, while the ground-based observatories recorded the intense auroral brightening and space currents over North America.

These observations confirm for the first time that magnetic reconnection triggers the onset of substorms. The discovery supports the reconnection model of substorms, which asserts a substorm starting to occur follows a particular pattern. This pattern consists of a period of reconnection, followed by rapid auroral brightening and rapid expansion of the aurora toward the poles. This culminates in a redistribution of the electrical currents flowing in space around Earth.

Solving the mystery of where, when, and how substorms occur will allow scientists to construct more realistic substorm models and better predict a magnetic storm’s intensity and effects.

More about Themis.

Original News Source: NASA press release

About 

Nancy Atkinson is Universe Today's Senior Editor. She also is the host of the NASA Lunar Science Institute podcast and works with Astronomy Cast. Nancy is also a NASA/JPL Solar System Ambassador.

Sasori July 29, 2008 at 1:06 AM

Lol THEMIS. Probably Dr Angelopoulos came up with that cause its a funny Greek name and he is Greek too.

Ignoramus July 29, 2008 at 6:37 AM

“Magnetic reconnection releases the energy stored within these stretched magnetic field lines, flinging charged particles back toward the Earth’s atmosphere”
Magnetic field lines do not physically exist. they are like contour lines on a map. How can they fling particles?

alphonso richardson July 29, 2008 at 6:52 AM

You’re right – contour lines don’t actually exist, but the physical quantity they represent – physical height relative to a known baseline(usually sea level) does.
Likewise (someone correct me if I’m wrong, please), the strength of magnetic flux, which the lines represent does exist. Field lines, like contour lines, simply provide a visual medium to convay physical quantities or effects.
I think.

Magneto July 29, 2008 at 1:19 PM

… a bit like claiming that a re-arrangement of contour lines, releases energy… instead of describing the actual physical process…. an earthquake. As Hannes Alfvén wrote:

“The most important criticism of the “merging” mechanism of energy transfer is due to Heikkila [40] who, with increasing strength, has demonstrated that it is wrong”

See: W. J. Heikkila, Astrophys. Space Sci., vol. 23, p. 261, 1973.

Hannes Alfvén, “Double Layers and Circuits in Astrophysics”, IEEE Transactions on Plasma Science Vol. PS-14 No.6 (Dec 1986)

Stephen July 30, 2008 at 12:17 AM

I wonder if the secondary phenomena such as “coronal loops” and “reconnection events” that occur during SUNSPOTS can now be more accurately predicted by using the Earth’s changes in Aurora activity? I bet the pattern of these emissions will be very more similar than they are expecting and lead to a better understanding of why radio waves are especially the most effected by these emmisions.

Are radio photons emmited by distant stars and novas during our high sun spot activity (distorted via the solar wind), could this lead to even more sensitivity to distortion by localized Aurora which charges particle via electromagnetic rebounding…thus a cummulative effect to a charged radio photon particle that leads to greater radio wave disruption…

a field of distorted radio photons trapped in earths atmosophere that were a process of sunspot, solar wind and magnetossphere reaction

alphonso richardson July 30, 2008 at 3:27 AM

Sorry M. Didn’t claim to be an expert, but it can take a while for people to get their head around somethings. Plus, I DID say that if I was wrong, for someone to correct me if I was.
Maybe you could proffer an explanation to Ignoramous that makes sense, not just scientifically, but in lay terms for clarity.

I’m (seriously) all for those with better understanding to communicate scientific ideas, as not everyone comes to the papers or these forums with assumed knowledge.

Places like these are perfect for this (Thanks Fraser, et al)

Bridh Hancock July 30, 2008 at 4:59 AM

“This pattern consists of a period of reconnection, followed by rapid auroral brightening and rapid expansion of the aurora toward the poles.”

This seems like quantum maechanics in action.

Q: Can this activity been seen, say, from Mars?
Q: Is there a South Pole equivalent?

Kootstar July 30, 2008 at 10:30 AM

I do not know about Mars view, but the aurora is basically the same N. pole and S. pole areas, the size, activity and longevity, from what my readings have told me. Hope you get to see some beauties like I have. There is nothing I can say to explain the feeling of watching that sky dance and glow in light and color,so much that you could read the fine print, IF you could just get your eyes off that sky!

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