Lightning bursts in clouds are responsible for clearing the enigmatic "safe zone" for satellites, lying between two doughnut-shaped radiation belts
surrounding the Earth, say NASA researchers. The discovery, announced on Tuesday, surprised space physicists who had not expected an atmospheric
phenomenon to affect a region 10,000 kilometres above the Earth's surface.
The Van Allen radiation belts were the first big surprise of the space age when US Explorer satellites discovered them in 1958. The pair of
doughnut-shaped rings consist of high-energy charged particles from solar outbursts and cosmic rays.
The inner ring extends between 1000 and 7000 km above the equator, while the outer ring starts at 13,000 km and extends to 25,000 km. The trapped
radiation imperils both humans and spacecraft, so satellites and astronauts fly above or below the radiation belts - or in the gap between them.
The Earth's magnetic field bends the paths of the charged particles, trapping them so they spiral back and forth along magnetic lines of force
stretching out between the poles. Solar outbursts pump more particles into the radiation belts, expanding the belts so they obliterate the gap. Yet in
a matter of days the charged particles drain from the gap, leaving the safe zone re-established once more.
Most space physicists had thought turbulence in the gap generated low-frequency radio waves that ejected the particles, but others thought the radio
waves might instead come from lightning.
To test the lightning theory, James Green of the NASA Goddard Space Flight Center compared maps of lightning activity collected by the Micro Lab 1
spacecraft with data on radio waves in the radiation-belt gap from the IMAGE spacecraft.
He found that the two patterns matched - increases in lightning preceded increases in radio-wave activity in the radiation belts. When intense solar
storms filled the gap with charged particles in November 2004, terrestrial lightning activity was low, and the gap took up to a week to reappear.
Lightning is known to generate low-frequency waves, which at low latitudes follow the curvature of the Earth for hundreds of kilometres as they are
reflected between the ground and the ionosphere - the Earth's upper atmosphere which contains charged particles.
However, radio waves generated by lightning at the high latitudes of the northern US, Canada, and Europe strike the ionosphere at a different angle,
says Green, allowing them to leak out into the magnetosphere - the region of space where the Earth's magnetic field dominates. "
This is an important discovery and perhaps it could be used to "harness" the energy natirally generated by out planet so we can stop "burning"