Re: Solar flares herald rare glimpses of northern lights over UK

http://www.guardian.co.uk/science/2011/feb/17/solar-flares-northern-lights-uk



Solar flares herald rare glimpses of northern lights over UK

At least three powerful solar flares on the sun have hurled billions of tonnes of material towards the Earth, which could light up the night sky in a spectacular aurora borealis



Solar flares on the Sun on 17 February 2011 View larger picture This image, captured in ultraviolet on 17 February 2011, shows the powerful solar flares that may lead to unusual displays of the northern lights. Photograph: Nasa/SDO

The surface of the Sun (above) erupts with dazzling solar flares that form giant, glowing loops reaching tens of thousands of kilometres into space.

Solar flares are the most violent explosions in the solar system and each releases as much energy as a hundred million hydrogen bombs. Earth-sized regions of the Sun's corona soar to temperatures of 20 million Celsius during the convulsions.

This image, captured by Nasa's Solar Dynamics Observatory (SDO), shows a storm brewing on the surface of the Sun over the past week. On Tuesday, satellites recorded the most powerful solar flare in four years erupting from a massive sunspot.

The storm generated at least three solar flares, the most intense of which was detected at 1.56am GMT on Tuesday. The x-class flare, the most powerful of all solar events, came from a growing active region called 1158 in the Sun's southern hemisphere.

The bright flashes were accompanied by coronal mass ejections, which blasted billions of tonnes of material towards the Earth at 900 kilometres a second. The rush of particles could light up the night sky with a spectacular aurora borealis, but cloud cover and the brightness of the moon may obscure the view.

The British Geological Survey said displays of the northern lights had already been seen further south than usual, in Northern Ireland and elsewhere in the UK. The celestial light show occurs when cosmic particles hit the upper atmosphere and are steered to the poles by the Earth's magnetic field, colliding with other particles.

The US National Weather Service warned that geomagnetic storms caused by the Sun's activity could disrupt GPS services and communications satellites for a day or two. The Chinese Meteorological Association reported that Tuesday's solar flare had already caused atmospheric disturbances that jammed radio communications in southern parts of the country.

In 1989, a coronal mass ejection knocked out the power grid in Quebec, tripping transformers and leaving six million people without power.

Solar flares occur when intense magnetic fields build up in the Sun's atmosphere and suddenly release their energy. The explosions produce vast amounts of radiation, from radio waves and visible light to X-rays and gamma rays.

The image shows the Sun through the SDO's ultraviolet camera, with solar flares looping out into space and back along lines of magnetic field. Solar flares contorted by magnetic fields can be seen in both hemispheres.

The Sun's activity rises and falls over an 11-year cycle and is expected to peak as it reaches the Solar Max in 2013. Solar flares are expected to become more common, and more intense, as the Sun's activity increases.
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