BALTIMORE — For centuries, scientists have looked up at the northern sky to see the colorful aurora borealis and wished they could see more. Thanks to the new Polar satellite, that wish has come true.
Traveling an orbit that arcs high over the North Pole, Polar's instruments let scientists see the entire auroral show. But this is more than celestial voyeurism. There are immediate earthly benefits to these observations. Understanding these storms could save utility and oil companies millions of dollars.
As the Northern Lights flash, they send 100,000-ampere electric currents throughout the northern upper atmosphere. The magnetic fields associated with those currents can reach down to induce electric currents that speed up corrosion of the 800-mile Alaska oil pipeline. Excited by outbursts of solar particles, the changing auroral fields can interact with the ground to knock out electric power transmission grids as far south as Texas.
If an aurora hits during a heat wave, when air conditioners and ice-cream makers force electric utilities to run at full capacity, the sudden magnetic surge could knock out the entire East Coast.
The ability finally to see what the aurora is doing through the Polar satellite has energized auroral scientists. "This is our golden opportunity ... to understand what we can predict, and how well we will be able to predict" auroral events that have such economically important impacts on the ground, said Louis Frank of the University of Iowa in Iowa City as he showed off some of Polar's first images during last week's meeting of the American Geophysical Union here.
Mario Acua of the NASA Goddard Space Flight Center in Greenbelt, Md., also stressed the importance of developing as enhanced a forecasting ability as possible in cooperation with the present National Space Weather Program that watches for solar storms. Even a half hour's warning could help utilities put their power transmissions systems in configurations that would make them less vulnerable. Better understanding of the whole auroral phenomenon would also help designers of future pipelines build in safeguards against corrosion.
Polar is one of a fleet of satellites in the International Solar Terrestrial Physics program. In that program, European, Japanese, and American satellites are monitoring the sun and the space environment around Earth. The aim is to understand how Earth responds to whatever the sun is throwing at us.
Like an embattled star ship in science fiction, Earth has its shield up to deflect the solar assault. As the solar wind sends electrified, magnetized particles, Earth's own magnetic field deflects the particles, creating a buffer zone between the planet and the solar wind.
THIS zone, called Earth's magnetosphere, has weak points over the North and South Poles. This is where the force lines of Earth's magnetic field connect to the planet. They form conduits by which charged particles can flow down into the atmosphere. There the particles interact with gases in the air to cause the Northern Lights. They also make the air electrically conducting so massive currents can flow. During solar-induced magnetic storms, the energy associated with this action is on the order of 100 million megawatts - enough to light up New York City.
Polar, which was launched Feb. 24, is in an orbit that ranges from 3,200 miles high over the South Pole to over 32,000 miles out from the North Pole. The satellite takes 17.5 hours to complete one revolution, with much of that time spent where it can see the northern aurora.
Polar has 11 instruments that measure particles and electromagnetic fields in the magnetosphere. For the first time, scientists are able to see both the nightside and the dayside sections of the aurora. The sun's glare washes out dayside aurorae in visible light. Polar's X-ray and ultraviolet eyes aren't affected by glare.