Polarized Northern Lights Detected in the Arctic
29.04.2008 - Other
An international team of scientists, lead by Jean Lilensten of the Laboratory of Planetology of Grenoble in France, has detected polarization in aurora borealis. This unexpected finding could provide new insight on the composition of Earth's upper atmosphere, the configuration of its magnetic field and the energies of particles coming in from the sun.
Aurora borealis are light emissions resulting from the interaction of charged particles in solar winds with the planet's magnetic field, which strike atmospheric gases.
Lilensten and his colleagues observed auroral lights during the winters of 2006-2007 and 2007-2008 from Svalbard, Norway. They detected the weak polarization of a red glow, radiating at an altitude of 220 kilometres. A polarized beam of light means the electromagnetic waves share a common direction. It had been suspected such light to be polarized because the Earth's magnetic field funnels electrons at high latitudes and aligns the angle at which they enter the atmosphere.
However, up until now, lack of evidence lead to generally admit that light emitted from energized atoms and molecules could not be polarized in planetary upper atmospheres.
This discovery fosters new scientific applications:
- Detection of polarization fluctuations could inform scientists on the energy of the particles that come in from the sun and enter the Earth's atmosphere;
- Polarization intensity could reveal upper atmosphere composition, especially regarding atomic oxygen;
- Magnetic field configuration could be determined;
- If polarization is observed on other planets, scientists could be offered clues on how the sun's magnetic field curves around other bodies and on the way it is distorted by obstacles such as planets Venus and Mars, which lack magnetic fields.
