Space used to be exactly that: void, empty nothingness. Not any more. It is now diffused with a tenuous charged gas of ponderous protons and high-speed electrons, whose supersonic motion is controlled by contorted electromagnetic force fields. These particles whirl about and react violently with planets and spacecraft. At Earth this solar wind can have a velocity of more than 1 million miles an hour, the particles having temperatures of more than 100,000 degrees. Even though there are only a few particles per cubic centimetre, the stormy interactions between this wind and our planet can be hazardous.
John Freeman is not only an expert on the Earth's magnetosphere, but also an accomplished writer. He has taken the rather esoteric topic of the plasma weather in our near-space environment and presented it in a gripping and easily understandable fashion.
He explains the dangers and consequences of extreme space weather using a series of fictionalised vignettes. Unprotected astronauts working outside a space station receive fatal doses of radiation; avionics systems crash demanding that aircraft autopilots be overridden; and satellites drift off station.
Freeman traces the causes back to the active Sun. Electrostatic discharges above bi-polar sunspot groups not only produce pulses of radio waves and X-rays but also lead to coronal mass ejections. Particles with energies of more than 1 billion electron volts charge towards the Earth. At the equator, the Earth's equatorial magnetic field deflects these particles, but at higher latitudes they pour into the upper atmosphere. Subsequently they can fall out of the lower cusps of the Van Allen belts, producing auroral displays. Under the auroral zone the magnetic fields can fluctuate violently, inducing currents in long power lines.
Freeman goes on to explain how features observed in one location can be used to parameterise models that predict what is happening in other regions. What is more important than this global "nowcasting" is the ability to forecast space weather, thus enabling precautions to be taken to mitigate hazards.
Storms in Space works on many levels. It is an engaging, well-illustrated, eminently readable layman's introduction to this important aspect of solar-terrestrial relations.
David W. Hughes is professor of astronomy, University of Sheffield.
Storms in Space
Author - John W. Freeman
ISBN - 0 521 66038 6
Publisher - Cambridge University Press
Price - £18.95
Pages - 139