new technology could save us from dangerous solar storms

How new technology could save us from dangerous solar storms
Simon Hadlington reports
Published: 06 June 2007
Independent UK

Solar eruptions can destroy satellites and leave cities in darkness - but we can't tell if we're in the firing line until it's too late. Now an early warning system is finally on its way.

Without the Sun there would be no life on Earth. But, as well as bathing us in light and warmth, the star at the centre of the Solar System has a darker side, and every so often it reminds us of its awesome force. In 1989, Quebec experienced a massive power cut, leaving six million people without electricity for 11 hours. The problem was caused by a violent magnetic storm in the Earth's atmosphere which originated some 150 million kilometres away - on the surface of the Sun. The star had sneezed, and on Earth, the lights went out.

The Sun is constantly releasing a stream of charged particles. This is called the solar wind, and it gently buffets the magnetic field that surrounds the Earth. Usually it has little effect - though it is responsible for the aurorae, the magnificent displays of light that can sometimes be seen in the night sky near to the poles - but occasionally the Sun's surface flares up and the wind becomes more powerful. And then there can be an even more violent occurrence: part of the outer atmosphere of the Sun, the corona, splits off into space, a powerful magnetic field with it.

Satellites are especially vulnerable to this kind of "space weather" and, across the world, scientists are trying to devise ways to predict when the Sun is likely to send out a dangerous burst of solar wind.

The key to preventing serious damage is knowing how the magnetic field of such a solar emission is aligned. If it is aligned in a particular direction, the consequences can be dire, as the residents of Quebec discovered. Currently, we can only spot this just half an hour before the magnetic storm hits Earth, as this is when it is detected by the Stereo spacecraft, which Nasa uses to monitor the Sun. This gives little notice to take any measures such as switching satellites to safe mode to prevent damage.

Now, however, scientists at the Massachusetts Institute of Technology in the United States think they may have the answer - by monitoring radio waves from several distant stars and galaxies. As the radio waves pass through a solar storm they are altered subtly depending on the orientation of the storm's magnetic field. By measuring these changes scientists should be able to calculate the field's orientation many hours before the storm reached the Earth. Current telescopes cannot do this, but a new one, named the Mileura Widefield Array, which is being built in Australia and should be ready by 2010, should be suitable. The researchers say, as it will be able to monitor stars across a broad area of sky.

Meanwhile, researchers in the UK are developing a deeper understanding of this solar activity, which centres on the Sun's own magnetic field, as Dr Sarah Matthews, the head of the solar physics group at the Mullard Space Science Laboratory in Surrey, explains. The key to this solar activity lies in the Sun's magnetic field, as she explains: "The Sun's magnetic field is in a state of constant flux. It is a bit like a bar-magnet that is rotating at varying speeds, and, as it rotates, it winds up the lines of magnetic field, and portions break through the surface." These manifest themselves as sunspots and are energetically unstable. When there is a high density of sunspots on the Sun's surface, there is a greater probability of the release of energy. This can result in a flaring of the surface of the Sun or, in some cases, the corona becoming detached and flung off at high speed. The greatest activity occurs roughly on an 11-year cycle, when there is a large increase in the number of sunspots.

A coronal mass ejection is a huge bubble of charged gas and magnetic field, weighing billions of tonnes, that breaks away from the Sun and travels through space at anything up to two-and-a-half thousand kilometres a second," says Dr Matthews. "The problem of these ejections hitting Earth is not a new phenomenon - the Sun has been doing this as long as it has been shining - but it is more important now because of the way we live has changed; we rely increasingly on satellite technology and power stations." Dr Matthews is working on ways to predict when such events might occur and whether they are likely to be significant or not.

"When there are a lot of sunspots, you could get many solar flares a day and we might see several events directed to the Earth over several weeks. In October and November 2003 and in January 2005 there were a number of active regions on the Sun's surface hurling these ejections every 10 to 14 days before going quiet again. At maximum activity it would not be unusual for maybe one coronal mass ejection to come towards the Earth every week, but these will not always have the correct magnetic field orientation to produce an effect."

There are a number of satellites observing the Sun's surface and taking measurements. These could provide clues to the Sun's behaviour. "I am involved with trying to understand how the flares and the coronal mass ejections are initiated and how they relate to one another," says Dr Matthews. "Sometimes we get one and not the other. I want to know what is the instability that causes this release of energy. Is there a unique set of conditions that will always lead to instability and can we predict when these events will occur by examining how the magnetic field of the Sun varies over time? If we knew that one of these events was coming we could put in place systems to mitigate against it - by putting a satellite into safe mode or preparing for the possibility of disruption to the electricity supply."

Meanwhile, Dr Richard Horne of the British Antarctic Survey in Cambridge studies what happens to high-energy particles from the Sun when they meet the Earth's own magnetic field.

"When the solar wind meets the Earth's magnetic field it can rip open the front of the field and transfer energy to it," says Dr Horne. This can result in the generation of electric currents that flow down into the atmosphere. The more powerful the wind, the greater the energy.

"There are some 250 to 300 satellites currently in orbit above the Earth," says Dr Horne. "These are mostly telecommunications satellites each costing around $250m [£125m]. They are expensive to insure. A satellite is a major investment."

Dr Horne's research has shown that solar activity can be correlated with minor malfunctions of satellites throughout their lives. "You can get many small malfunctions, such as corrupted memory and phantom commands, though total failure of a system is relatively rare. But small problems can accumulate over the lifetime of a satellite."

On one occasion in 2003 - dubbed the Hallowe'en storm - more than 30 satellites reported malfunctions, coinciding with a major coronal mass ejection.

Solar storms can also have other impacts; for example they can disrupt the part of the atmosphere called the ionosphere, which is used in telecommunications to reflect signals that are bounced around the globe. Power supplies can be interrupted when the influx of highly charged particles into the Earth's atmosphere causes changes in the Earth's magnetic field, which in turn can set up large electric currents in power cables - as happened in Quebec in 1989. Oil and gas pipelines can also be affected. Operators often maintain metal pipelines at a slightly different electrical voltage to the Earth to prevent electrochemical corrosion of the metal. Even relatively mild solar activity - solar sub-storms - can disrupt this. But now Dr Horne's team is developing models of the way that solar wind interacts with the various regions above the Earth's surface to pinpoint the conditions that would be likely to give rise to significant events.

Does this affect climate change?

Scientists are pondering a possible link between "space weather" and long-term climate patterns. "In the past people have generally regarded the Sun as a constant," explains Dr Richard Horne. "But with a big solar event such as a coronal mass ejection you get a huge increase in charged particles that can leak into the atmosphere at high latitudes and change chemistry.

"In polar regions the nitrogen oxides that have been created descend in a special pattern called the polar vortex. At these levels the nitrogen oxides can deplete ozone, which is important for the way in which temperature is controlled, in the upper atmosphere. This can change the structure of the atmosphere at higher latitudes and this could, ultimately, have a wider effect on the way that the atmosphere is heated and cooled, which in turn has an impact on wind patterns.

"We are not saying that this phenomenon is responsible for global warming, but we are saying that this is possibly another mechanism by which the Sun can influence climate, which has not yet been quantified."