Featured Research

from universities, journals, and other organizations

Northern Lights Glimmer With Unexpected Trait

Date:
April 26, 2008
Source:
American Geophysical Union
Summary:
Some light in Earth's aurora glow is polarized -- a state not thought possible for the aurora, new observations indicate. The findings may improve understanding of Earth's upper atmosphere, its magnetic field, and the energies of particles from the Sun. If detected also in the atmospheres of the other planets, such polarization may help map the Sun's extended magnetic field, researchers say.

The glow of Earth's aurora is polarized, an unexpected state for such emissions. Measurements of this newfound polarization in the Northern Lights may provide scientists with fresh insights into the composition of Earth's upper atmosphere, the configuration of its magnetic field, and the energies of particles from the Sun.
Credit: iStockphoto/Andrew Dawson

An international team of scientists has detected that some of the glow of Earth's aurora is polarized, an unexpected state for such emissions. Measurements of this newfound polarization in the Northern Lights may provide scientists with fresh insights into the composition of Earth's upper atmosphere, the configuration of its magnetic field, and the energies of particles from the Sun, the researchers say.

If observed on other planets, the phenomenon might also give clues to the shape of the Sun's magnetic field as it curls around other bodies in the solar system.

When a beam of light is polarized, its electromagnetic waves share a common orientation, say, aligned vertically, or at some other angle. Until now, scientists thought that light from energized atoms and molecules in planetary upper atmospheres could not be polarized. The reason is simple: in spite of the low number of particles at the altitudes concerned (above 100 kilometers (60 miles)), there are still numerous collisions between molecules and gas atoms. Those collisions depolarize the emitted light.

Fifty years ago, an Australian researcher, Robert Duncan, claimed to observe what looked like polarization of auroral light, but other scientists found that single observation unconvincing.

To revisit the question, Jean Lilensten of the Laboratory of Planetology of Grenoble, France, and his colleagues studied auroral light with a custom-made telescope during the winters of 2006-2007 and 2007-2008. They made their observations from Svalbard Island, Norway, which is in the polar region, at a latitude of 79° north.

At the north and south magnetic poles, many charged particles in the solar wind --a flow of electrically charged matter from the Sun--are captured by the planet's field and forced to plunge into the atmosphere. The particles strike atmospheric gases, causing light emissions.

Lilensten and his colleagues observed weak polarization of a red glow that radiates at an altitude of 220 kilometers (140 miles). The glow results from electrons hitting oxygen atoms. The scientists had suspected that such light might be polarized because Earth's magnetic field at high latitudes funnels the electrons, aligning the angles at which they penetrate the atmosphere.

The finding of auroral polarization "opens a new field in planetology," says Lilensten, who is the lead author of the study. He and his colleagues reported their results on 19 April in Geophysical Research Letters, a publication of the American Geophysical Union, or AGU.

Fluctuations in the polarization measurements can reveal the energy of the particles coming from the Sun when they enter Earth's atmosphere, Lilensten notes. The intensity of the polarization gives clues to the composition of the upper atmosphere, particularly with regard to atomic oxygen.

Because polarization is strongest when the telescope points perpendicularly to the magnetic field lines, the measurements also provide a way to determine magnetic field configurations, Lilensten adds. That could prove especially useful as astronomers train their telescopes on other planetary atmospheres. If polarized emissions are observed there as well, the measurements may enable scientists to understand how the Sun's magnetic field is distorted by obstacles such as the planets Venus and Mars, which lack intrinsic magnetic fields.

Journal reference:  Lilensten, J., J. Moen, M. Barthιlemy, R. Thissen, C. Simon, D. A. Lorentzen, O. Dutuit, P. O. Amblard, and F. Sigernes (2008), Polarization in aurorae: A new dimension for space environments studies, Geophys. Res. Lett., 35, L08804, doi:10.1029/2007GL033006.


Story Source:

The above story is based on materials provided by American Geophysical Union. Note: Materials may be edited for content and length.


Cite This Page:

American Geophysical Union. "Northern Lights Glimmer With Unexpected Trait." ScienceDaily. ScienceDaily, 26 April 2008. <www.sciencedaily.com/releases/2008/04/080425123355.htm>.
American Geophysical Union. (2008, April 26). Northern Lights Glimmer With Unexpected Trait. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2008/04/080425123355.htm
American Geophysical Union. "Northern Lights Glimmer With Unexpected Trait." ScienceDaily. www.sciencedaily.com/releases/2008/04/080425123355.htm (accessed July 28, 2014).

Share This




More Earth & Climate News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) — The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
The Carbon Trap: US Exports Global Warming

The Carbon Trap: US Exports Global Warming

AP (July 28, 2014) — AP Investigation: As the Obama administration weans the country off dirty fuels, energy companies are ramping-up overseas coal exports at a heavy price. (July 28) Video provided by AP
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) — A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) — A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins