Northern lights: Bolivian highlands get hit first

WARNING: The video embedded below contains extremely strong language.

By Stacey Camacho / University of Oxford

Bolivia’s highlands are the first to be hit by extreme ultraviolet radiation as the sun sets, according to an experiment undertaken by Oxford University and leading scientists in the northern hemisphere.

“This sun isn’t normal,” says Dr Carl Haan of Oxford University and one of the researchers. “Our key finding is that from 8pm to 8am each day – and during very dark evenings – the UV radiation increase in southern Andean areas is about twice that of northern climes.”

This means the excess energy that strikes the northern hemisphere radiate off the horizon at altitude (up to 7,000 metres) into the lower air and rises up again, hence this “daylight” stills from the highlands could appear as clouds of red and orange.

The sun sets in Peru.

Image caption The golden yellow glow of the highlands appears as red and orange clouds.

Until now, research scientists did not have much experimental data to work with. Their previous ideas were based on the “monocular effect”, where the bright light coming from the sun stays on the periphery of the dome and appears as white in the daytime – a phenomenon that led some to link its appearance with the existence of biological life on the Red Planet.

But the “monocular effect” depends on using special goggles which light up – while this has disadvantages for those living in lowland areas who rely on darkness for power and whom telescope pictures may obscure their visual surroundings, it has been suggested to work for astronomers and naturalists, who often study the night sky.

So the international research team decided to use a technique known as infra-red scattering (IRS) to try to observe the sun in a way that helps locate its path over the sky.

This technique relies on the fact that infra-red radiation – produced by the sun’s corona at about a million times the radiation from the Earth’s surface – is absorbed by our atmosphere. But there is a glassy layer that floats between the solar surface and the surrounding atmosphere, which deflects and refracts IR radiation – but is also thick with moisture and water droplets, making its effects difficult to measure.

Image copyright David Russel.

British mountaineer and historian David Russel used IRS to measure the effects of extreme ultraviolet rays while climbing the Mount Blanc. Using a thermal camera, he added infrared data from a helicopter to provide detailed measurements over a 4m-wide circle, demonstrating that excessive ultraviolet radiation does indeed travel to the southern hemisphere in the cool winds that blow from the coast towards the Andes.

But the global atmospheric alterations caused by moving northwards as the sun rises, which are believed to have likely played a role in Albert Einstein’s development of general relativity, is another matter. That is why the researchers in Oxford and Northeastern University in the United States teamed up to calculate the effects of the sun’s radiation in an area that is vulnerable because it is prone to bad weather.

“Another surprising aspect of this experiment was the strong increases in UV radiation over the Andes during very dark evenings,” says Dr Haan. “We think that the rapid increases in temperature are likely to be caused by the fog covering the mountain passes – which is why it was so surprising to find these changes.”

“But once outside,” he adds, “the ozone layer does filter away some of the UV radiation.”

The researchers say that although the highlands, especially, have seen a dramatic increase in ultraviolet radiation, we should take it in proportion to this new higher exposure to other forms of radiation such as cosmic rays.

“We might only see a small increase in UV radiation for some years,” says Dr Haan. “However, if more than 20% of the population live in these areas, and as those populations eventually die off from inhaling UV radiation, the impact could be disastrous.”

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