On the day before Halloween last year, 20,000 homes in the city of Malm, Sweden, lost power. Authorities attributed the blackout to a surge of current in the power lines. The culprit, apparently, was a huge storm of cosmic origin striking the earth. A series of such storms in October and November forced airlines to reroute polar flights, shut down two Japanese satellites, and sent the aurora borealis dancing in skies as far south as Texas and Arizona.Magnetic storms happen about twice a year, when eruptions on the surface of the sun send streams of highly charged gas, known as coronal mass ejections, hurtling toward Earth at six million to eight million kilometers per hour. The first three to six hours of a storm-a storm can last two or three days-are the most intense, as the ejections disrupt Earth’s atmosphere and cause communication trouble for the ever increasing numbers of satellites, radios, and cell phones in constant use. “The amount of our technologies that are affected has been growing and growing,” says Jeffrey Hughes, director of the Center for Integrated Space Weather Modeling at Boston University.
The chances for a severe storm are greatest during the solar maximum, a period of heightened sunspot activity that recurs every 11 years. The last solar max occurred in 2000, so another one isn’t due until 2011. But in October and November of last year, conditions in the sun’s turbulent atmosphere brought about the solar equivalent of a late-season blizzard, and Earth experienced some unusually strong magnetic storms.
Alerted to the danger by a spacecraft monitoring the sun, John Foster, associate director of MIT’s Haystack Observatory in Westford, MA, began tracking the storms’ activity with the observatory’s two radar dishes dedicated to upper-atmospheric research. He and other atmospheric scientists have been trying to understand how the disturbances evolve, and how activity on the sun eventually affects the space environment around Earth. MIT observations have already helped show, for the first time, how charged particles belonging to Earth’s upper atmosphere are redistributed during a solar storm. Computer models calculate the particles’ behavior based on multiple variables, including the influence of the solar wind and the orientation of the sun’s magnetic field.
Foster has also been gathering data on these and other variables to take the research further. He has a theory that the intensity of a storm’s effect on the earth can be predicted in part by what time of day it strikes the planet. The episode recorded that night in October supported his argument, and if his theory proves right, it can help improve space weather forecasts. That could give industry and government officials plenty of notice to minimize the effects of the disruptions. “The work that he is doing is central to the observational side of our understanding of magnetic storms,” says Kile Baker, program director for magnetospheric physics at the National Science Foundation, which underwrites some of Foster’s research.