The forecasters from space

DANNY PENMAN

Scientists are on the verge of forecasting sunstorms in space which cause major disruption to communications, throw compasses off course and even spark explosions.

The first step to predicting surges in the solar wind - a stream of charged particles blowing outwards from the sun - will be taken next Thursday when the European Space Agency (ESA) and Nasa launch a new satellite to study the Sun. Early next year four other satellites will be launched as part of the same programme.

Earth's magnetic field normally shields the surface of the planet from the effect of solar storms. However, several times a year, sunstorms and the resultant increase in "solar wind" causes surges in the Earth's protective shield. The massive changes in the magnetic field can knock out communications satellites, cause electricity black-outs and interfere with television and radio broadcasts.

In March 1989, a huge solar storm blacked out half of Canada's electricity grid and put magnetic compasses out by up to 70 degrees, causing chaos for shipping and aircraft who relying on them for navigation.

Oil and gas industries are also concerned about the effects of the solar wind. The fluxes in the earth's magnetic field can produce electrical currents that can trigger explosions. The greatest danger oil workers face is corrosion, which can be increased by electric currents coursing along metal pipelines because of magnetic field changes.

At least one gas pipeline explosion, which claimed hundreds of lives, is thought to have been the result of this type of electrically induced corrosion. More than 650 people were killed when a fireball engulfed two trains on the Trans-Siberian gas line in June 1989.

The first satellite will go under the name Soho - the Solar and Heliospheric Observatory. The pounds 400m satellite will blast off from Kennedy Space Center and will travel 1.5 million kilometres towards the Sun where it will hang exactly balanced between the gravitational pull of the Sun and the Earth.

The satellite, to which Britain has contributed more than pounds 40m, contains a battery of detectors which will allow scientists to build up a detailed picture of the internal structure of the Sun, its atmosphere and composition of the solar wind.

Some of its telescopes, tuned to detect ultraviolet rays, may reveal what heats the corona, the Sun's atmosphere, and drives the solar wind. Particle detectors will link the gusts in the solar wind to upheavals in the Sun's surface.

Another detector, known as Golf, will monitor the rhythmic movements on the Sun's surface caused by massive sound waves as they pass through the star.

Using the same principles as seismology, where the pattern of a sound's movement through a solid can reveal details of its internal structure, as with earthquakes, scientists hope to probe the insides of the Sun. Golf will be able to detect movements on the Sun's surface as low as 1mm per second within a background movement of 0.5 km per second.

Professor Douglas Gough, leading the team who will interpret the seismic data from Soho, said it would be the equivalent of listening to someone whispering in a hurricane from 500 yards.

The next step to forecasting will be taken early next year, when the other four satellites, known as Cluster, will be launched. Cluster will monitor the effect of the solar wind on the Earth's magnetic field in three dimensions.

Scientists hope that once the effects of magnetic changes on the Earth and satellites can be linked to precise events on the Sun, and within the solar wind, they can start to make accurate solar weather predictions within five years.