We are increasingly hearing about the possible danger of ‘Space weather’, but what is it? And what harm can it cause?
THE sun is no simple light bulb. Far from being a static, albeit bright, blob of burning gas the sun is dynamic and mutable. Similar to Earth it also has its own peculiar types of season: the solar cycle. This is measured by the number of spots on the sun’s surface and, like human adolescence, could mean trouble. Unlike humans, however, more spots on the sun means more activity, and a greater chance of chunks of its surface being sloughed off and hurled towards Earth.
On March 9th 1989, at the height of a solar cycle, a massive burst of charged particles called a Coronal Mass Ejection (CME) was released from the sun, directly towards Earth. Four days later the lights in Québec went off. This kind of event is not so out of the ordinary for the sun, but the effect here on Earth is becoming increasingly bothersome.
A solar cycle typically lasts for about 11 years, give or take, and NASA expects the current cycle – cycle 24 – to peak sometime in 2013. As Dr Maggie Aderin-Pocock, a Space scientist from Imperial College London, puts it, “We’re going through a few rough years of space weather but it should settle down after that.” The cycles are caused by fast moving ‘winds’ of gas and plasma deep within the sun.
The sun, being a ball of gas, doesn’t spin at a fixed rate like the solid Earth; it rotates faster at the equator than at the poles. This creates a dynamo effect, winding the sun’s magnetic field up and storing energy; sun spots are a symptom of this increasingly tightening magnetic field.
Sun spots typically mark the areas where CMEs and solar flares – a sudden brightening and release of energy and particles – occur. An average CME can eject almost 1.6 thousand billion kilograms of matter into space at speeds of up to four million miles per hour. When one of these is aimed directly at the Earth, the increased amount of charged particles is the genesis of ‘space weather’.
The sun is constantly emitting these particles, but usually far fewer and much, much slower. This is the solar wind, a constant feature of our solar system.
Playing with magnets
It’s the extra energetic particles from a CME and their interaction with Earth’s atmosphere and magnetic field that caused the problems in Québec.
Earth’s magnetic field is generated by electric currents flowing through its molten iron outer core. Without it acting like a shield our ozone layer would be stripped away, allowing dangerous levels of UV light through, and eventually our atmosphere would be almost completely blown away by the solar wind. The charged particles from the sun meet the magnetic field and are ushered gently and safely around the Earth.
The real problem for us starts when there are enough of these high-energy particles that – from a CME for example – the sheer number and energy of the particles creates a shock wave. This compresses the sun side of the Earth’s magnetic field and stretches out the ‘dark’ side of the field behind the Earth. When this happens the particles can be funnelled through the magnetic field to the poles in the Earth’s upper atmosphere. This gives rise to the beautiful ‘aurora borealis’ towards the north poles, and the ‘aurora austrialis’ in southern regions.
The wonderful moving greens, reds and blues are caused by the high-energy particles colliding with atoms in the upper atmosphere and exciting them. As they return to their normal state they release light. Aurora can make the otherwise invisible magnetic field visible. However, there is also a sinister side to this rapidly changing magnetic field. It can induce an electric current in long conductors. Long conductors are typically things like power lines or, more worryingly, the steel pipelines used to transport high pressure liquid or gas.
The sudden extra voltage induced by the CME in March 1989 caused the Hydro Québec power grid to fail in a matter of seconds, as protective relays tripped leading to a cascade of events that took 9 hours to resolve, leaving nearly six million people and businesses without power. The economic cost was thought to be in the region of millions.
Of course, Space weather isn’t just a problem on Earth. Over the years we’ve thrown quite a few bits of technology, and people, into orbit. Dr Jonathan Eastwood, also of Imperial College London, says that the most recent event on March the 6th 2012 “could cause intermittent satellite navigation [GPS] and HF [high frequency] radio problems, especially in more polar regions, as well as bright auroral displays in northern regions.”
This didn’t pose quite such a threat in recent history, since during the last solar maximum the world wasn’t as dependent on satellite communications – mobile phones and GPS – all technologies that could be disrupted by solar flares and CMEs. A recent risk report on the subject of space weather by Lloyds, the syndicated insurance market, noted that the failure in 2010 of Intelsats Galaxy-15 spacecraft was likely due to space weather.
The report goes on to state that, “If the spacecraft is eventually declared a total loss, there will be a substantial capital loss: Galaxy-15 was barely four years into an operational life that is typically ten to ﬁfteen years. Given that the typical cost of a comsat is around $250 million, this loss is likely to be over $100 million.”
Dr Craig Underwood, deputy director of the Surrey Space Centre, University of Surrey, said that, “Such events act as a wake-up call as to how our modern western lifestyles are utterly dependent on space technology and national power grid infrastructure.”
Concerns over GPS aren’t as simple as finding yourself instructed to drive over footpaths or non-existent bridges. GPS is increasingly the only navigation system used by super tankers and aircraft. Ships could find themselves stranded at sea with no accurate idea where they are. Airplanes would be grounded until the situation could be resolved. GPS is also used to time-stamp financial transactions in stock markets the world over.
If GPS were severely impacted, global trading would have to cease. If this went on for any period of time it could lead to a global economic crisis as the flow of money between countries and institutions dries up.
However, governments and scientists are not standing idly by waiting to see what happens. “Space engineers go to some lengths to ensure that spacecraft can continue to operate under these hostile conditions. Similarly, space scientists are working hard to try to understand the physics of these events, so that we may be able to give more warning of when such an event is likely to occur,” states Underwood.
Observing the sun can let us see when CMEs and solar flares are heading for us, which gives us a few days to prepare, but, for now, it seems all we can do is sit back and wait to see what happens.
Note: This was written as part of a portfolio for MSc, in this case written to be in the style of an article for the Economist. Not sure the tone is quite there, but, well, feel free to let me know what you think.