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THE NORTHERN LIGHTS: BEAUTY OR BEAST? The beauty of the Aurora Borealis – or Northern Lights – is world famous and like nothing else. Caused by charged particles from space colliding with gas particles in the Earth’s atmosphere at 40 million miles per hour, the spectacle can only be seen in the Arctic (and the Southern Lights in the Antarctic). The aurora brings huge amounts of power into the atmosphere – typically about 50 gigawatts. That’s more than the daily electricity consumption of the UK (which was an average of 30.5 gigawatts last year, according to the National Grid). But what impact is the aurora and its impressive energy having on our planet, and how does it affect our climate? These are the questions Dr Dan Whiter, NERC Research Fellow, is addressing through his latest work.
of the Earth’s atmosphere, at the edge of space, from about 100km upwards. Thermal imaging Through his fellowship, Dan is developing his unique technique of using sensitive cameras equipped with colour filters. The spectrum of certain auroral emissions depends on the temperature of the atmosphere, so he is using his images to make maps of atmospheric temperature, similar to a thermal imaging camera.
To find the answers, Dan needs to be able to measure the temperature of the atmosphere at auroral heights – something that has never been done effectively as it’s an altitude that’s notoriously difficult to reach. It’s too high for weather balloons, but too low for spacecraft.
The temperature maps will be combined with radar measurements of the upper atmosphere to estimate the electrical conductivity. Dan is then using a computer simulation to understand how different types of aurora are produced, what electric currents they generate, and how the aurora affects the temperature and chemistry of the upper atmosphere.
Last year, he won a five-year fellowship from the Natural Environment Research Council to develop a novel technique to study how the aurora affects the temperature and chemistry of the upper atmosphere. The upper atmosphere is the outermost layer
He’s using the University’s camera system, ASK (Auroral Structure and Kinetics), in Svalbard. ASK has three cameras and has been operating since 2007, automatically taking images whenever it’s dark. ASK is located at the site of the EISCAT Svalbard
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Radar, a radar system for measuring the ionosphere (charged part of the upper atmosphere). Dan said: “In Svalbard, very high up, we have cameras and a spectrograph to measure the temperature of the upper atmosphere. The cameras have telescopes on top to take images of a small area of the sky in great detail.” This area is approximately 100km up in the sky, and 12 times the size of the moon as viewed from the ground. “This allows us to look at a very small scale to see the heating around different types of aurora shapes and what they do to the atmosphere,” added Dan. “We’re trying to establish how much heating there actually is and how it’s structured. It could be very concentrated in a small region. In terms of chemistry, you could get production of nitric oxide, which could affect the atmosphere more widely, for example through destruction of ozone. It’s not known yet.” He explained that some heating is certainly occurring – enough that weather forecasters are taking an interest.