21:13 03Dec2003 Cracks let solar wind disrupt Earth's atmosphere


WASHINGTON, Dec 3 (Reuters) - The solar wind pries open immense cracks in the Earth's magnetic
field, holding them apart while it gushes through to cause geomagnetic storms, scientists reported
on Wednesday.
The findings could help scientists better predict the storms, which can disrupt power,
satellites and communications and endanger astronauts, the U.S. space agency NASA said.
"We think we have solved an old and long-standing controversial discussion of how this process
of crack formation really works," Harald Frey of the University of California, Berkeley, who led the
study, told a news conference.
"Now that we know these cracks do not just open and close sporadically ... but can stay open for
a long and extended time of several hours ... we can go on and incorporate this knowledge into our
next step of modeling space weather impacts."
The findings, published in this week's issue of the journal Nature, were made using the orbiting
IMAGE satellite, designed to watch the Earth's protective magnetic layer or magnetosphere. A group
of four satellites called Cluster detected the charged solar particles streaming through.
"It is critical for us to understand where, when, and for how long the magnetic shield is
breached and how this energy gets in," said Janet Kozyra of the University of Michigan, a space
weather expert who did not work on the study.
This information "will help us to make more accurate space weather predictions."
The Sun regularly spews out charged gas called plasma in what is known as a coronal mass
ejection. "Our magnetic shield takes the brunt of space storms, but some energy continually slips
through its cracks, sometimes enough to cause problems with satellites, radio communication, and
power systems," Frey said.
"The only things that humans can really see in a magnetic storm are the aurora lights," Kozyra
added.
The space storms can dump 1,000 billion watts into the atmosphere while they last -- more than
the total electric generating capacity of the United States.
IMAGE -- the Imager for Magnetopause to Aurora Global Exploration -- revealed an area of heavy
particles called ions almost the size of California hitting the ionosphere above the Arctic region.
"This aurora, energetic enough to power 75,000 homes, was different from the visible aurora
known as the Northern and Southern lights," NASA said in a statement.
"While the aurora was being recorded by IMAGE, the 4-satellite Cluster constellation flew far
above IMAGE, directly through the crack, and detected solar wind ions streaming through. Normally,
these solar wind ions would be deflected by Earth's shield, so Cluster's observation showed a crack
was present."
The researchers estimated the the crack was twice the size of the Earth at a point 38,000 miles
(60,000 km) above the planet's surface. Such cracks evidently open all the time, said Nancy Crooker
of Boston University.
Several monster solar storms hit the Earth last month but caused little disruption. When
officials know they are coming they can move satellites and prepare power grids to minimize the
effects.