Scientists to explore what they know about space weather
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More than 100 scientists from the United States and other nations will gather next week in Guntersville, Alabama, for the 6th biennial conference on the magnetosphere sponsored by NASA's Marshall Space Flight Center and the University of Alabama at Huntsville. It will be a significant meeting, surveying what's been learned in the last few years with the International Solar Terrestrial Physics (ISTP) program, and looking ahead to unique instruments that will be launched in the year 2000 and beyond to reveal even more.
"We've gone from just trying to learn what's out there - the plasma sheet, the plasmasphere, the ring current, and so on - to understanding how they work and affect each other," said Dr. Dennis Gallagher, member of the conference program committee.
The process started 40 years ago with the launch of Explorer 1 on Jan. 31, 1958, and its discovery of the Van Allen Radiation Belts. Almost every flight after that discovery found something new.
"Over the last 10 years we've shifted our focus from discovering features to discovering processes," Gallagher said. "To some extent, we're doing what weather people did before they got their first satellite images of weather. We are trying to understand better how things work."
Space weather is shaped by two fundamental forces, the solar wind blowing outward from the solar corona, and the Earth's magnetic field which shields the planet and makes the wind flow around it.
Mankind has long enjoyed - or feared - the most obvious effect of the shoving match between these two forces. The aurora borealis, or northern lights (and the aurora australis, as explorers later found) forms when electrons spiral down along the magnetic field lines and slam into the outer atmosphere.
Unsuspected until the Space Age was the magnetosphere, an immense, ghostly body of plasmas (gases stripped of electrons) in the shape of a comet, squeezed towards the Earth on the sun side and dragged out about 2 million kilometers away on the night side.
"We began the Huntsville workshops to highlight the importance of thermal plasmas in the magnetosphere at a time when that population was largely ignored," Gallagher said. Thermal plasmas are considered to be cold, but only by comparison to energetic plasmas. They still have temperatures of nearly 200,000 degrees Fahrenheit!
Above: One of the mysteries of the magnetosphere that will be discussed at the Guntersville workshop is how much of the magnetosphere is filled by the polar auroral fountain - gases energized and accelerated upward from Earth's atmosphere - and how much is provided by the solar wind.
"They were somewhat ignored because early researchers tended to think that the behaviors of thermal plasmas were easily explained, so they focused on the behavior of the more energetic plasmas," Gallagher continued. "The ring current, plasma sheet, solar wind, and other components were considered movers and shakers because they were a source of energy to make things happen. But it turns out that their lives are greatly influenced by the thermal plasmas."
The thermal plasmas act like a sponge, absorbing energy from more energetic plasmas. They even reduce the frequencies of radio noise that "rings" along magnetic field lines, as if a piano wire had made itself heavier.
"The magnetosphere is dominated by cold plasmas," Gallagher said. "It's become more apparent that they are important for energy transportation and other processes that occur in the magnetosphere."
In addition to scientific curiosity, magnetospheric studies are important to understanding space effects that can damage or even cripple communications and other satellites, and disrupt communications and power systems on Earth. This research culminated in recent years with the International Solar Terrestrial Physics (ISTP) program which put satellites into orbits that probed the solar wind, the magnetic tail and everything in between.
Much of the Guntersville conference will review what's been learned in recent years, and will also look at future missions, like the Imaging Magnetospheric Explorer (IMAGE) satellite, that will give these scientists what meteorologists have had with weather satellites.
|New Millennium Magnetosphere Conference Agenda, including speakers.
MSFC Space Plasma Physics home page links to news, instruments, and other neat stuff.
Surprising gap in aurora borealis puzzles scientists Oct. 16, 1998.
Odd auroral arc crosses rather than circling the North Pole May 29, 1998.
"If anyone looks at a satellite image they can say, Oh, that's a hurricane'," Gallagher said. "We don't have that because we've only been able to take our measurements as if we'd been standing in the storm with rain and wind gauges. These new missions will take us to a whole new level of understanding - and questions."
Stay tuned. We'll be reporting daily from the conference.
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Author: Dave Dooling
Curator: Bryan Walls
NASA Official: John M. Horack