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First global connection between Earth and space weather found (Forwarded)



 
 
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Old September 13th 06, 01:27 PM posted to sci.space.news
Andrew Yee[_1_]
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Default First global connection between Earth and space weather found (Forwarded)

Bill Steigerwald / Ed Campion
Goddard Space Flight Center, Greenbelt, Md. Sept. 12, 2006
301-286 5017 / 0697

RELEASE: 06-75

FIRST GLOBAL CONNECTION BETWEEN EARTH AND SPACE WEATHER FOUND

Weather on Earth has a surprising connection to space weather occurring
high in the electrically-charged upper atmosphere, known as the
ionosphere, according to new results from NASA satellites.

"This discovery will help improve forecasts of turbulence in the
ionosphere, which can disrupt radio transmissions and the reception of
signals from the Global Positioning System," said Thomas Immel of the
University of California, Berkeley, lead author of a paper on the
research published August 11 in Geophysical Research Letters.

Researchers discovered that tides of air generated by intense
thunderstorm activity over South America, Africa and Southeast Asia
were altering the structure of the ionosphere.

The ionosphere is formed by solar X-rays and ultraviolet light, which
break apart atoms and molecules in the upper atmosphere, creating a
layer of electrically-charged gas known as plasma. The densest part of
the ionosphere forms two bands of plasma close to the equator at a
height of almost 250 miles. From March 20 to April 20, 2002, sensors on
board NASA's Imager for Magnetopause to Aurora Global Exploration
(IMAGE) satellite recorded these bands, which glow in ultraviolet light.

Using pictures from IMAGE, the team discovered four pairs of bright
regions where the ionosphere was almost twice as dense as the average.
Three of the bright pairs were located over tropical rainforests with
lots of thunderstorm activity -- the Amazon Basin in South America, the
Congo Basin in Africa, and Indonesia. A fourth pair appeared over the
Pacific Ocean. Researchers confirmed that the thunderstorms over the
three tropical rainforest regions produce tides of air in our atmosphere
using a computer simulation developed by the National Center for
Atmospheric Research, Boulder, Colo., called the Global Scale Wave
Model.

The connection to plasma bands in the ionosphere surprised scientists at
first because these tides from the thunderstorms can not affect the
ionosphere directly. The gas in the ionosphere is simply too thin.
Earth's gravity keeps most of the atmosphere close to the surface.
Thunderstorms develop in the lower atmosphere, or troposphere, which
extends almost 10 miles above the equator. The gas in the plasma bands
is about 10 billion times less dense than in the troposphere. The tide
needs to collide with atoms in the atmosphere above to propagate, but
the ionosphere where the plasma bands form is so thin, atoms rarely
collide there.

However, the researchers discovered the tides could affect the plasma
bands indirectly by modifying a layer of the atmosphere below the bands
that shapes them. Below the plasma bands, a layer of the ionosphere
called the E-layer becomes partially electrified during the day. This
region creates the plasma bands above it when high-altitude winds blow
plasma in the E-layer across the Earth's magnetic field. Since plasma is
electrically charged, its motion across the Earth's magnetic field acts
like a generator, creating an electric field. This electric field shapes
the plasma above into the two bands. Anything that would change the
motion of the E-layer plasma would also change the electric fields they
generate, which would then reshape the plasma bands above.

The Global Scale Wave Model indicated the tides should dump their energy
about 62 to 75 miles above the Earth in the E-layer. This disrupts the
plasma currents there, which alters the electric fields and creates
dense, bright zones in the plasma bands above.

"The single pair of bright zones over the Pacific Ocean that is not
associated with strong thunderstorm activity shows the disruption is
propagating around the Earth, making this the first global effect on
space weather from surface weather that's been identified," said Immel.
"We now know that accurate predictions of ionospheric disturbances have
to incorporate this effect from tropical weather."

"This discovery has immediate implications for space weather,
identifying four sectors on the Earth where space storms may produce
greater ionospheric disturbances. North America is in one of these
sectors, which may help explain why the U.S. suffers uniquely extreme
ionospheric conditions during space weather events," Immel said.

Measurements made by NASA's Thermosphere Ionosphere Mesosphere
Energetics and Dynamics (TIMED) satellite from March 20 to April 20,
2002, have confirmed that the dense zones exist in the plasma bands.
Researchers now want to understand whether the effect changes with
seasons or large events, like hurricanes.

The research was funded by NASA. The National Center for Atmospheric
Research is sponsored by the National Science Foundation, Arlington, Va.
For a list of participating scientists and related images, please visit
on the Web:

http://www.nasa.gov/centers/goddard/...ther_link.html
 




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