Week 15: 'I would like to apologise to many of my friends for being so occupied...'

Wonder spawned in: 2011
Wondered into being by: The Sun, the Earth, and Ole Salomonsen
Wonderspan: 5 min
To experience this wonder at its best: Click on the full-screen icon.

Let's talk about the weather in space, where it's sunny with clear skies but always windy.

The Sun is spinning off a stream of electrically charged particles that spiral outwards in waves like a flamenco-dancer's skirt.  The particles form fronts of space weather travelling at a million kilometers per hour.  This is the solar wind.

The solar wind would be harmful to life were it not for the Earth's magnetic field, which emanates from the excitation of matter in the planet's spinning, molten core.  The field's force lines form their own shape, like a giant iris flowering around the Earth.  Its sun-side petals push most of the solar wind outwards, around the planet and off into space, but the field also pulls some of the wind back towards the Earth just below each pole.

Electrons from the solar wind striking particles in the Earth's upper atmosphere give them an electrical charge, which they can then dump by emitting light.  So, although it's not normally visible to the naked eye even at night, a constant glow, called a diffuse aurora, hangs above the poles.

But the solar wind is gusty, too.  Squalls of particles buffet and compress the Earth's magnetic field, affecting how it pulls them them towards the Earth.  On a windy day in space, the solar wind billows the upper atmosphere as if it were a linen sheet hanging out to dry.  If we happen to be in the right place, we get to watch the solar gusts create green, red, yellow, blue and purple waves of light in the sky.  The colour depends on whether oxygen or nitrogen particles are being struck, and how high in the atmosphere they are.  These light shows are the northern lights (aurora borealis) and southern lights (aurora australis).

A space breeze becomes a storm when the sun releases solar flares and/or throws out large dollops of highly energised matter from its corona.  When these storms reach Earth they cause radio 'scintillation' and electrically excite power lines, electronics and a whole host of other stuff we rely on.  In the largest solar storm on record in 1859, telegraph operators were able to carry on a conversation with all the power turned off, by using only the excitation of the cables by the electrons from the solar wind.  These storms also interfere with the magnetite (a magnetised mineral) which homing pigeons and several other animal species use to navigate.

These storms also squeeze and weaken the Earth's magnetic field, which then brings the solar wind down to the atmosphere at much lower latitudes.  In the geomagnetic superstorm of 1989, people were watching aurorae in Texas, for example.

The field is measured constantly based on data from a few geomagnetic monitoring stations dotted about the planet.  The readings from last month show a 100 nano-Tesla dip in the field strength on 9 March, which classifies that day's space weather as an 'intense' storm.  This was caused by the sun throwing off two large waves of plasma earlier in the month. It would have been a good night for aurora-watching if Europe had been facing away from the sun at the time.

From space the aurorae appear as huge halos around the poles - here's a short video of the International Space Station crossing the southern lights.  (There are more aurora videos from NASA here but do come back!)

It's harder to find good video of the aurorae from the ground but one man, Ole Salomonsen from Tromso in Norway, spent six months taking 50,000 stills of the northern lights and splicing them together into this film to reflect as closely as possible their real-time movement.  He writes:

'In the video I have put together a collection of slow moving auroras in the woods, over the mounatins, in the city, in the foreshore, reflected in the sea, with some of the most spectacular and strongest auroral outbreaks seen in many years. Included here is a coronal outbreak, in which I am particularly happy to present, since it is very difficult to get on stills, even worse on "film".

'I could never have done this without the fantastic understanding and help from my girlfriend. This has been an insanely time-consuming project. Both hours after hours out in the cold, but also all the hours in post-processing during late nights has led to a severe lack of sleep.  Also, I would like to apologize to many of my friends for being so occupied the last months. Looking forward to spend more time with you all now.'

Today Ole (and vicariously, also his girlfriend Veronica) bring a little northern wonder into our offices (it's probably better without the sound, by the way):

• http://vimeo.com/21419634

Receive aurora alerts for the UK or out-nerd your friends by making your own auroral detector! Sign up at http://aurorawatch.lancs.ac.uk

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And can you help, please?

Later in the year I want to feature some street musicians/dancers/artists on waysofloving.com - I'm particularly interested in unusual forms - musicians playing unusual instruments, for example.  If you have any suggestions - good quality sound/image if poss - then please let me know.  Email justplaindavid@waysofloving.com.  Ta v much.

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