|
 February 24, 2000
-- Imagine tuning in to the local TV weather report and hearing
this from the weatherman:
"Good evening space weather lovers! Last night Earth was
hit by a high-pressure solar wind stream. It's expected to persist
for 3 or 4 more days producing a 50% chance of mid-latitude aurora.
If you were hoping to use your cell phone today -- forget it!"
One day, space weather forecasts like this could be commonplace.
As our society comes to rely on satellites, cell phones, and
other space-age gadgets, forecasting solar and geomagnetic storms
can be just as important as knowing the chances of rain tomorrow.
Unfortunately for technophiles, space weather forecasting is
about 40 or 50 years behind everyday weather predictions.
Right: A cutaway diagram of the magnetosphere
illustrates how IMAGE will observe the magnetosphere. For more
information, visit the IMAGE home pages at the Southwest
Research Institute and the Goddard
Space Flight Center.
A new NASA mission to explore Earth's magnetic space
environment may change that. Scheduled for launch on March 15,
2000, the "Imager for Magnetopause-to-Aurora Global Exploration"
(IMAGE for short) is a spacecraft designed to study the global
response of the Earth's magnetosphere to changes in the solar
wind.
The magnetosphere is an area of space around our planet that
is controlled by Earth's magnetic field. It helps keep out charged
particles from the solar wind, including high-energy particles
that come from solar flares and coronal mass ejections. The magnetosphere
is not a perfect shield. When the Sun is very active, ionized
gas is able to penetrate the magnetosphere and high-pressure
solar winds can cause the magnetic field to be squeezed and buffeted.
During periods of gusty solar wind, powerful magnetic storms
cause vivid auroras, radio and television static, power blackouts,
and navigation problems for ships and airplanes with magnetic
compasses. There can even be damage to satellites and spacecraft.
Predicting these events can be tricky, and often impossible,
because scientists don't yet have a global view of how the magnetosphere
works. During the past 40 years, space physicists have made many
individual measurements of conditions at different points in
the magnetosphere, but the overall picture of plasmas, fields,
and flowing currents is missing.
"It's a little like looking at a thermometer in Alaska,
checking the barometric pressure in Florida, and then trying
to predict the weather in Europe," explains Dennis Gallagher
(NASA/MSFC), an IMAGE Co-investigator responsible for the theory
and modeling activity, and a member of the Radio Plasma Imager
science team. "Assembling a global picture from a statistical
collection of data is dicey. We've never been able to step back
and see the whole thing. All of the instruments on IMAGE provide
unique and wholly new ways of looking at the magnetosphere."
IMAGE is such a cutting-edge mission that it has been named as
a semifinalist in two award competitions: Discover Magazine's
Innovative Technology of the Year Award for 1999 and the Columbus
Foundation Award.
Left: IMAGE will be placed in an
orbit that loops high above the Northern Hemisphere to provide
wide views of the aurora borealis and the inner magnetosphere.
The elliptical orbit will precess during the 2-year mission.
To get the best view of this new frontier, IMAGE will be launched
into an orbit that loops from a low point of 1,000 km (600 mi)
to a high point of almost 45,000 km (almost 27,000 mi). From
that vantage point, IMAGE's instruments will look back and be
able to see the inner structure of the magnetosphere, including
the magnetopause, the boundary where the magnetosphere meets
interplanetary space.
Instruments on IMAGE include:
- The Radio Plasma
Imager. The RPI will use radar echoes in the frequency range
3 kHz to 3 MHz to detect and monitor ionized gas (plasma) inside
the magnetosphere.
- Far Ultraviolet
Imager. The FUI will take pictures and spectra of the entire
Earth along with the auroral oval at ultraviolet wavelengths.
The 3 instruments that combine to form the FUI instrument package
(GEO,
SI
and WIC)
will provide almost constant monitoring of auroral activity from
above our planet. The Earth is surrounded by a cloud of neutral
atoms and molecules that is largely invisible from the ground.
The so-called 'geocorona' is an extension of Earth's atmosphere
into space. It is mostly made up of hydrogen, because it's the
lightest element. GEO will also be used to detect these neutral
atoms, measure their energy and map their distribution.
- Neutral
Atom Imagers. The neutral atom cameras will detect neutral
atoms created by ring
current ions and escaping auroral
ions that collide and exchange charge with the cold, geocoronal
hydrogen gas. This will allow scientists to indirectly monitor
and explore the ring current and auroral ion fountains.
- Extreme
Ultraviolet Imager. The EUVI will detect ultraviolet photons
from the Sun that are scattered by helium ions in the plasmasphere,
a torus of cold dense plasma surrounding the Earth in the inner
magnetosphere. A sophisticated deconvolution technique will be
used to translate the photon counts into images of the plasmasphere.
 With these instruments in orbit, scientists
will have a whole new view of the space around Earth. And they're
not the only ones. The data from IMAGE will be posted to the
web in near real-time for viewing by the public as well as by
scientists. Unlike some other missions, IMAGE data will not be
considered proprietary to the mission scientists for any length
of time. For the first time in history, anyone with an internet
connection will be able to watch the magnetosphere in action.
Right: Click
the image for a 3D simulation of the magnetosphere's shape.
The Sun is off screen to the left. The animation begins showing
the Earth, which recedes as the shape and size of the magnetosphere
comes into view. The solar wind deforms the magnetosphere into
its characteristic shape. Where the magnetosphere and the solar
wind meet is the "bow shock," represented in the animation
by a faint, translucent bullet shape. Credit: Digital
Radiance
"Just think about how geosynchronous weather satellites
changed things for meteorologists," said Gallagher. "Nowadays
you can show anyone a satellite picture of a hurricane and they'll
say, 'hey, that's a hurricane!' Now imagine how our field will
change when we can look at pictures of ring currents, the plasmasphere
and the magnetopause and watch them change in real time."
Science@NASA will follow this story with a series of science
articles leading up to the launch of IMAGE, currently scheduled
for March 15, 2000.
|
Parents and Educators: Please visit
Thursday's
Classroom for lesson plans and activities related to this
story. |
For more news and information about space weather, please see
SpaceWeather.com.
Technical information about current space weather conditions
may be found at the NOAA Space
Environment Center. |
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