NORUSCA II camera sheds new light on auroras
By Darren Quick
November 29, 2012
Even those of us not lucky enough to have witnessed them in person will likely have marveled at photos of the stunning auroras caused by high energy particles from the Sun colliding with atoms in the Earth’s atmosphere. A team of space-weather researchers has now developed a new camera called NORUSCA II that has produced the first-ever hyperspectral images of the aurora borealis (or northern lights) and may have uncovered a previously unknown atmospheric phenomenon.
Until now, even the cameras used to capture images of the auroras for scientific analysis have collected all the light together in one image. This meant that researchers looking to analyze specific bands or a small portion of the spectrum would need to use a series of filters to capture a series of images.
The NORUSCA II takes a similar approach, but using advanced optics it can achieve the same result with no moving parts ... and much, much faster. The camera can switch between all of its 41 separate optical bands in a matter of microseconds, allowing specific bands of the auroras to be combined into one image.
“A standard filter wheel camera that typically uses six interference filters will not be able to spin the wheel fast enough compared to the NORUSCA II camera,” said Fred Sigernes of the University Centre in Svalbard (UNIS), Norway. “This makes the new hyperspectral capability particularly useful for spectroscopy, because it can detect specific atmospheric constituents by their unique fingerprint, or wavelengths, in the light they emit.”
The researchers say the NORUSCA II’s multispectral imaging capabilities will shed new light on the way the Earth responds to solar storms by allowing scientists to better classify auroras from background sky emissions and study the way they cluster in the atmosphere.
The camera’s inaugural research campaign may have already revealed a previously unknown atmospheric phenomenon. A Coronal Mass Ejection (CME) resulting from a major solar flare on January 24, 2012, eventually slammed into the Earth’s magnetic field, providing a perfect chance for the team to fully test the camera. This was done at the Kjell Henriksen Observatory (KHO) in Svalbard, Norway.
Even through a layer of low altitude clouds, the camera was able to produce images of unprecedented clarity that revealed something the team didn’t expect – a very faint wave pattern of unknown origin in the lower atmosphere resembling what is known as an "airglow."
Airglow is a natural optical phenomenon involving the very weak emission of light by the Earth's atmosphere. It was already known that airglow could be caused by various processes in the upper atmosphere, including cosmic rays striking the upper atmosphere, or chemical reactions, such as oxygen and nitrogen reacting with hydroxyl ions. However, the wave pattern’s appearance at the same time as the aurora has led the researchers to believe it may also be caused by a previously unknown source. If confirmed, it would be the first time that airglow has been associated with auroras.
“After the January CME, we think we saw an auroral-generated wave interaction with airglow,” said Sigernes. “Our new all-sky camera opens up new frontiers of discovery and will help in the detection of auroras and the understanding of how our Sun impacts the atmosphere here on Earth. Additional development and commissioning will also hopefully verify our intriguing first results.”
Details of the NORUSCA II camera and the results from its first images were published this week in the Optical Society’s (OSA's) open-access journal Optics Express.
Source: The Optical Society