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Sciences Research: The space weather forecast

The International Geophysical Year of 1957 had a straightforward aim of studying the Earth as a planet during a period of intense solar activity. Half a century on, and now we are in the International Heliophysical Year (IHY), which will see a further celebration of our local star, where satellites and space probes will be centre stage. Roger Highfield explains

The ‘Heliosphere’ is a reference to the area of space in which we live – the area of influence or the Sun. The aim of the IHY – actually two years, as if to reflect the enthusiasm of astronomers – is to raise awareness of the relationship between the Sun and the Earth and also to drive a programme of collaborative research in a field that endlessly reminds us that our Earth is not an isolated object.
 

Space weather

A regular solar armada

In recent years, an armada of satellites has set out to study the Sun.

Solar and Heliospheric Observatory (SOHO)
One of the most important solar missions to date has been the Solar and Heliospheric Observatory (SOHO) , jointly built by the European Space Agency and NASA, with British involvement, and launched in 1995. Originally a two-year mission, SOHO has now operated for over ten years (as of 2007). It has proved so useful that a follow-on mission, the Solar Dynamics Observatory , is planned for launch in 2008.

THEMIS
Another mission that will provide new data is NASA’s THEMIS mission to study the aurorae, launched in February. The mission – which consists of five satellites – will help resolve the mystery of what triggers geomagnetic substorms. Substorms are atmospheric events visible in the northern hemisphere as a sudden brightening of the Northern Lights ( Aurora Borealis ).

Other missions
Other missions include Hinode , formerly known as Solar-B, which is a Japan Aerospace Exploration Agency solar mission, in collaboration with the US and the UK.

Closer to home, the Earth’s shield – the magnetosphere – is studied by Cluster satellites, and Eiscat (an acronym for the European Incoherent Scatter Scientific Association in Norway, Finland and Sweden) studies the interaction between the Sun and the Earth as revealed by disturbances in regions of the atmosphere, the ionosphere and magnetosphere.

And NASA is planning for an expected maximum of solar activity between 2010 and 2012. One idea is to dot new probes, called sentinels, in key spots like inside the orbits of Venus and Mercury, near the Earth and on the farside of the Sun. Together with other spacecraft, this would provide a complete picture of the Sun.

Few of us realise that there are two kinds of weather. One is familiar: rain, sun, snow and that kind of thing. The second is space weather. The Sun produces the solar wind – a stream of charged particles that blows across the planets of the solar system, including the Earth. Whilst the Earth’s magnetic field protects us from most of the effects of this wind, we still experience the consequences of massive events on the Sun, both as a threat to satellites and power systems, and as the beautiful aurorae seen at the poles. 

On the Sun’s turbulent surface, there are active regions where there are flares (releases of energy in the form of light) and violent ‘burps’ of plasma (charged particles). They are associated with each other, but are very different, like volcanoes and earthquakes, according to Professor Richard Harrison of the Rutherford Appleton Laboratory (RAL) in Oxfordshire. They both tend to occur in the same active regions on the Sun’s surface, but the jury is still out as to whether you need one to produce the other.

But they are the subject of intense study because the largest flares can be linked with the biggest bangs in the solar system, sending out up to ten million times more energy than that released from a volcanic explosion. These ‘coronal mass ejections’ (CMEs) can carry up to ten billion tons of charged particles, travelling at speeds as high as 1,250 miles per second. A cloud can move at a million miles per hour and can cause havoc.
 

Keeping your health in space

In his 1970s book, Space , the US novelist James Michener depicted a fictional Apollo manned space mission that loses its crew to radiation this way. This concern still resonates today. The Earth’s magnetic field gives the planet and its inhabitants a good measure of protection, but, with space agencies seemingly intent on sending astronauts to the Moon and even to Mars in the next few decades, there is a pressing need for a deeper understanding of the Sun’s activity.

Moon or Mars bases will have to be carefully designed shelters, and astronauts will need very good advice before deciding to venture too far from such protection. To find out if astronauts could be driven mad by radiation exposure during a Mars mission, the US space agency recently launched a £7.5m study. The possibility that massive amounts of solar and cosmic radiation will damage the brains of astronauts, if they survive the mission at all, is among the most grave and has been dubbed ‘Risk 29’ by Nasa’s Mars scientists.

Although it is possible to use shields to defend the occupants of a spacecraft from radiation in a kind of fallout shelter, it could make the craft too heavy to reach Mars, given that, at its closest, it is 38 million miles from the Earth and that propellant is the largest contributor to the overall mass of a spacecraft.

A dozen teams have been commissioned to determine the human brain’s maximum safe cosmic radiation dose and to decipher precisely how radiation causes cognitive impairment, part of a quest for biological countermeasures to reduce radiation-related cognitive impairment. This research may not only help make it safer to go to Mars, it could lead us to a deeper understanding of how the brain functions,’ says one of the principal investigators, Dr Richard Britten, a Briton now working at Eastern Virginia Medical School in Norfolk, Virginia. ‘That eventually could help patients dealing with conditions that cause dementia.’

The use of radiation to treat children with ringworm decades ago had produced ‘very worrying’ results which showed it could impair cognitive function and increased the likelihood of ending up in a mental institution, he says. Astronauts ‘may have some serious problems during the flight and when they get back, with an accelerated Alzheimer’s scenario’.

The scientists hope to determine how much shielding the spacecraft and astronauts will need, and also develop other countermeasures that to help reduce radiation-induced brain damage. British scientists are planning to see whether a Star Trek-style deflector shield, based around magnetic fields, could be built to protect astronauts from radiation. ‘You don’t need much of a magnetic field to hold off the solar wind. You could produce the shield 20–30 kilometres away from the spacecraft,’ explains Dr Ruth Bamford from the Rutherford Appleton Laboratory.

Closer to home

But the effects can be felt here, too. The cloud of plasma from one of these cosmic burps is laced with magnetic fields and if these have the proper orientation, they can dump energy and particles into the Earth’s own magnetic field, causing magnetic storms that can overload powerline equipment and radiation storms that disrupt satellites. Satellite and utility operators can take precautions to minimise damage, but they need an accurate forecast of when space weather will arrive, which is anything from minutes to days, depending on the kind of radiation. (Energetic particles and radiation from solar flares reach the Earth in a matter of minutes, the slower-moving material from a mass ejection usually takes days.)

The Earth’s upper atmosphere also becomes more ionised and expands, altering the transmission of radio signals and sometimes disturbing satellite orbits because of greater drag from the expanded atmosphere. Satellites’ electronic components can be damaged and radio blackouts occur. In extreme cases, such storms can induce electric currents in the Earth and oceans that can interfere with or even damage electric power transmission equipment for the reasons given above.
 

The STEREO spacecraft

To find out more, NASA’s (Solar Terrestrial Relations Observatory) STEREO spacecraft went into operation for the first time this year. The two observatories are orbiting the Sun, one slightly ahead of Earth and one slightly behind, separating from each other by approximately 45 degrees per year.

Just as the slight offset between your eyes provides you with depth perception, this separation of the spacecraft allows them to take 3D images and particle measurements of the Sun.

The solar weather originates in the Sun’s atmosphere or corona. The corona is translucent, like a ghost in an old movie, and it flows along the Sun’s tangled magnetic fields, so it sometimes looks like spaghetti gone wild. It is hard for scientists to tell which structures are in front and which are behind. Images from the SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) telescopes on each spacecraft are being combined to create the 3D views.

Britain has a key role in this mission. The detectors for all the STEREO cameras were built at the Science and Technology Facilities Council’s Rutherford Appleton Laboratory in the UK, which is also co-ordinating the IHY’s science programme. Dr Chris Davis from RAL says: ‘It is a tribute to UK engineering that these wonderful 3D images are only possible because of the detector systems developed here.’
 

Sunshine


As if to underline the importance of the Sun, it even starred in a recent sci-fi film written by Alex Garland and directed by Danny Boyle. In it is 2057 and the Earth is freezing over. The Icarus II is sent on a suicidal mission to deliver a vast nuclear device to reignite our Sun, which is dying. There is one key flaw in the film. When its hydrogen fuel runs out, our Sun will indeed eventually swell 200 times its present size into a red giant. The only problem is that its demise is estimated to occur in around five billion years, not fifty, as in Garland’s screenplay. He was inspired to write the script, a meditation on the power of nature and how the Sun nourishes life on Earth, by scientific ideas about what is called the ‘heat death’ of the Universe – when it has run down to a thin, cold cosmic gruel incapable of supporting life.

The HI (Heliospheric Imager) cameras on the spacecraft were built by a consortium that included the Rutherford and the University of Birmingham. HI has a broad field of view and will be studying how the solar burps propagate, particularly those that are likely to affect the Earth. Professor Harrison, principal investigator of the HI instruments and Head of Space Physics at the Rutherford, said: ‘Understanding the complex processes that happen in our Sun is a big challenge. Using the two eyes of our STEREO spacecraft, we are able to see in three dimensions, allowing us to understand the relative positions of matter around the Sun and measure more precisely where the front of a CME is.’

STEREO ’s depth perception will also help improve space weather forecasts. Dr Chris Eyles of the University of Birmingham says it will allow scientists to study the 3D structure of a cloud sent out by a mass ejection ‘and predict in advance which ones will cause serious magnetic storms with the potential to cause problems on Earth’. In parallel, a new tool is being investigated at the Rutherford Lab to alert scientists to these ejections so they can be tracked along their journey to the Earth using the STEREO spacecraft. The tool identifies regions that have dimmed as a result of the expelled material, using ultraviolet imaging of the solar atmosphere to pinpoint the birth of the ejected clouds. 

Coronagraphs – instruments that block the solar disk to reveal the clouds – are best suited to viewing sideways ejections, not those aimed towards Earth. Thus, previous imagery did not show the front of a solar disturbance as it travelled towards Earth,
so scientists had to make estimates of when the storm would arrive. And these estimates can be very uncertain, perhaps by a day or so, or failing to predict them at all. With the STEREO spacecraft able to look back at the Earth and Sun, and the space between, scientists can for the first time track the front from the Sun all the way to Earth, and forecast its arrival within a couple of hours.

A good start

A great solar burp was captured the STEREO spacecraft almost as soon as its instruments went into operation at the start of this year. Professor Harrison comments: ‘It is wonderful for the UK that we are able to deliver these first dramatic pictures right at the start of IHY’.

Dr Lucie Green of UCL’s Mullard Space Science Laboratory is also involved in the IHY in the UK. She explains: ‘The more we understand about the way the Sun relates to its environment, the better we can protect humanity from this “space weather”.’

Unlike its predecessor, this Year marks a period of relatively low solar activity (which gives a chance to look at isolated events without a confusing roar of background noise). But the hope is that, when the activity of our nearest star peaks in five years, the Earth will be better prepared for the worst of solar weather. As Professor Harrison puts it: ‘With STEREO , we have just started and it is great that this marks the beginning of IHY with a new chapter in solar-terrestrial research.’

Roger Highfield was Science Editor of The Daily Telegraph newspaper and is now Editor of New Scientist magazine.

Read other science research papers, including 2006 research about a New Zoonosis Centre and research from 2008 on Harnessing Power From Nature.