Scientists observing solar storms with a soft x-ray telescope on board the orbiting Japanese Yohkoh satellite have found a direct link between the solar eruptions and magnetic storms in Earth's upper atmosphere.
"This is the first time that we have been able to see these high temperature regions at the center of the Sun in x-ray images," said Dr. Hugh Hudson, an astronomer at the University of Hawaii, during an international conference on magnetic storms held Feb. 12-16 at NASA's Jet Propulsion Laboratory.
"The Sun's outer atmosphere, the corona, dims just before these particles are ejected, allowing us to watch the bright flow of material as it is flung into space," Hudson told physicists, power and utility company representatives and members of the Department of Energy's national laboratories. "It's this dimming signature in the Sun's corona that tells us a magnetic storm is on the way."
All of the causes of magnetic storms originate at the Sun, researchers reported at the weeklong conference, co-sponsored by the American Geophysical Union and the National Science Foundation. The particle storms begin when large amounts of coronal mass break away from the Sun and travel rapidly toward Earth.
"Magnetic storms are caused by abrupt, intense events on the Sun, which impact Earth's magnetic field," said Dr. Bruce Tsurutani, a plasma physicist at JPL and co-convener of the conference. "If we can predict that these storms will occur, certainly we will be able to reduce the cost of damage on Earth."
New observations at latitudes above and below the Sun's equator point to that possibility. Scientists observing these events as they occur can give industries hardest hit, such as the power and electric utilities, 50 to 70 hours of advance warning that a magnetic disturbance is imminent.
"These releases of great amounts of the outer corona travel very rapidly toward Earth, at thousands of kilometers per second and, in some cases, tens of thousands of kilometers per second," explained Dr. Douglas Hamilton, a professor of physics at the University of Maryland. "Magnetic clouds take two to three days to arrive at Earth."
Major disturbances from the Sun erupt about every three to four years, resulting in widespread power blackouts. The most severe in recent years struck in 1989, when an outage in the Quebec province almost shut down the entire northeastern U.S. grid as well, said John Kappenman, an engineer at Minnesota Power.
Sometimes the collisions produce auroras, shimmering curtains of light in the northern and southern hemispheres. Other times they create large fluctuating currents that wreck havoc with technologies on the ground. Kappenman said that with a few days advance notice, power and utility companies could mitigate damage by shutting down transformers or redirecting power through alternate grids.
Once the storms enter Earth's ionosphere, they alter the composition of the Van Allen radiation belts, Hamilton said. During intense solar storms, large amounts of electrically charged oxygen are drawn out of Earth's upper atmosphere and become part of the radiation belts.
"We once thought that the Van Allen radiation belts were made up of electrons and protons, the simplest subatomic charged particles, but we know now that in these very large storms, a vast amount of electrically charged oxygen is drawn into them and can intensify the belts by a factor of 10 to 20," Hamilton said.
"We're learning that the Earth is not just a passive bystander getting buffeted by clouds of solar gas," he said. "Rather, the Earth itself, the very tenuous upper reaches of the atmosphere, contain a lot of electrically charged matter that contributes new particles to the Van Allen belt."
North America is, by far, the most vulnerable to magnetic fluctuations, Kappenman added. The landmass is closest to Earth's magnetic north pole and outranks other industrial centers as having the largest and most complex power grids.
A recent power industry study, spanning 25 years of magnetic storms, revealed correlations between disturbances in the upper atmosphere and blackouts at power plants from Maine to California, he said.
"Rock geologies in North America are extremely vulnerable to these magnetic storms because they complicate or add coupling effects to power systems," Kappenman said. "The failures are occurring in fairly large numbers and we see patterns in failure rates in different parts of the country."
New England, for example, has a transformer failure rate that is 60 percent higher than other regions of the country due to its geological composition. The Pacific Northwest, similarly, revealed a transformer failure rate 48 percent higher than other regions of the U.S.
"These power outages are one of the biggest nightmares we live with in the power industry," Kappenman said, "in that the duration of an outage could be several hours, possibly extending into days. The cost to industry well exceeds $100 million in failed equipment alone. These storms not only hamper critical public services but cause life threatening situations."
NASA is participating in the international Solar-Terrestrial Physics program to launch new spacecraft to study space weather for the benefit of human life. With new spacecraft such as Polar and the Advanced Composition Explorer, researchers believe storm forecasting will reach new levels of accuracy and allow industries enough time to safeguard communities all over the world.
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