Those of you who were in the UK as far south as Gloucestershire and South Wales during late February this year may have been lucky enough to witness the incredible aurora borealis lighting up the night sky - it's very rarely seen so far south. Although I missed this event (being even further south in Turkey at the time), I experienced a huge display of the 'northern lights' a couple of years earlier on visit to Tromso in northern Norway, with slowly rippling sheets of glowing green clearly visible even from the heart of the street-lit city. Despite their ethereal and mesmerising beauty, such dramatic events are actually a manifestation of the frighteningly powerful magnetic forces within our sun, and a reminder of our vulnerability to its unpredictable and violent nature, particularly in this modern technological age.
Do you remember in science lessons making a pattern with iron filings around a bar magnet? The earth behaves just like that bar magnet, with magnetic field lines curving around it into the north and south pole. This strong magnetic field,which protects us from many harmful space emissions, also deflects fast moving electrons flowing from the sun, sending them north and south towards the poles. Here they follow the field lines towards the poles, passing down into the upper atmosphere, where they react with oxygen and nitrogen molecules. The exchange of energy between the falling electrons and the gas molecules causes the glow of the aurora, with the different gases causing different colours.
The sun, our nearest star, emits a steady flow of such particles (the 'solar wind') and produces auroral displays on a regular basis.
However, the sun is actually turbulent ball of constantly twisting and snapping magnetic fields and from time to time enormous solar flares erupt from its surface, catapulting plumes of radiation and charged particles into space. These are sometimes accompanied by huge exploding bubbles of gas and magnetic fields, known as Coronal Mass Eruptions (CME).
This image shows the same CME at two different times on the same day (the central dark circle is part of the coronagraph observing instrument that masks the bright disc of the sun so that the surrounding corona is visible).
When these events occur in the direction of the earth, our home is bombarded with a 'Solar Storm' of high speed, high volume radiation, charged particles and magnetic fields. The upside is that auroral displays become more spectacular and extensive. However, the downside is potentially catastrophic for our civilization – communication and navigation systems may be disrupted, satellites and power lines may be damaged, and radiation exposure for anyone flying at altitude is increased.
Scary stuff indeed in a highly technology-dependent civilization like ours!
Faster than a speeding bullet!
Even more worrying, at present we have no way of predicting when these events will occur. All we can do take precautions after solar observatories in space spot them happening. But the warning time is very short - radiation from solar flares reaches earth in less than 9 minutes, and although the particles from CMEs are slower, they still take less than 5 days to reach us.
Clearly there is an urgent need for a 'Space Weather Forecast' system!
The key to better prediction is research into the internal processes of the sun, and this is a key goal for solar scientists.
The US-based NOAA space-weather prediction centre and the UK Met Office have been collaborating for several years, aiming to improve predictions, based on work by scientists who model solar activity and compare the models with actual observations from satellites and spacecraft.
Only last week the UK Met Office announced the creation of a UK-based 'Space Weather Operations System' which will see them collaborating internationally as a regional warning centre for severe events.
It's reassuring to see that this threat is being taken seriously, although there is clearly a long way to go.
But in between worrying about the chance of being zapped by radiation from a solar flare during a flight, or having our phones and power systems scrambled by a geomagnetic storm, do take time to sit back and appreciate the surreal beauty of the aurora that's also a result of the violent power of our sun.
And finally, it's fascinating to see that the aurora is not just exclusive to Earth – it can occur at other planets with a strong magnetic field and atmosphere. Check out this image of the aurora around Saturn's north pole, captured by my favourite space mission, Cassini.
Next week: Exploding stars!
For more information:
Images of the Aurora in southern UK: http://www.bbc.com/news/uk-26378027
Coronal Mass Eruptions: http://solarscience.msfc.nasa.gov/CMEs.shtml
FAQs about solar storms: http://www.nasa.gov/mission_pages/sunearth/spaceweather/#q22
National Ocean and Atmospheric US-based space-weather predictionsystem: http://www.noaanews.noaa.gov/stories2011/20111019_spaceweather.html
UK Met Office space-weather announcement (6th May 2014) http://www.metoffice.gov.uk/publicsector/emergencies/space-weather/met-office-role
Image credits:
Aurora: Creative Commons
Earth's magnetic field: NASA/Goddard Space Flight Center Scientific Visualization Studio
Coronal mass eruption: SOHO ESA and NASA
Solar flare: http://www.nasa.gov/content/goddard/20140329-sun-emits-x1-solar-flare/#.U2-ngSjDt-A
Aurora and sunrise: http://www.nasa.gov/mission_pages/station/multimedia/gallery/iss030e177670.html
Saturn's aurora: NASA/JPL/University of Arizona