Enormous
bubbles of plasma trapped within Earth's magnetic fields have been fully mapped
for the first time.
Scientists
now think the bubbles of ionized gas, called convection cells, are strongly
affected by pummeling from the sun's solar wind. Future observations of the
cells could be used to monitor violent solar outbursts, such as solar flares
and coronal mass ejections, which can harm satellites or astronauts in space.
"The
results are a great achievement," said Philippe Escoubet, the European Space
Agency (ESA) project scientist for the experiments aboard the Cluster satellites.
Stein
Haaland, a scientist at the Max Planck Institute in Germany,
and his team used six years of data gathered by the four spacecraft to
create the maps. "They show data collected over years is helping deepen
our understanding of the Sun-Earth connection," Escoubet said.
Convection
cells exist high above Earth's polar caps and are made of plasma, which is
electron-stripped gas that is highly erratic. Earth's magnetosphere and
atmosphere shelter the planet from high-energy solar particles, but the
protective shells form an incomplete cocoon—so some of the radiation leaks in,
is trapped and forms convection cells.
Scientists
think understanding how such particles are trapped is crucial to safeguarding
astronauts and satellites, such as GPS and telecommunications platforms.
Prior to the
Cluster satellites, only poor observations of convection cells
could be made. The new statistical maps show that numbers of convection cells
fluctuate between two and four, and that their shapes change as solar wind
output fluctuates.
Haaland said the maps will
inform future monitoring of convection cells. "It will be possible to map
the region at any altitude, under any conditions with satellites, making our
task easier," he said.
Haaland and his colleagues' work is detailed in recent issues of the journal Annales
Geophysicae.
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