The sun, in a periodic show of its force, is shooting off powerful solar flares that disrupt the Earth's magnetic force and could cause power shortages in the Northern United States over the next week and spark a display of the northern lights visible as far south as Maryland.
This is a sun storm, and government scientists monitoring it in Boulder, Colo., have classified it as "severe," the category designating the highest degree of force.
The last severe solar storm, in March 1989, caused power blackouts in northern New York and Canada. Damage, however, is hard to predict, experts say. There could be almost no noticeable effects, but an alert is on for the next week as the sun rotates and its most active region turns to face Earthmore directly.
"We don't know why" the sun goes through this cyclical pattern, Joseph W. Hirman, manager of the Space Environmental Services Center in Boulder, said yesterday. "But you can tell what's happening. We can measure it."
Mr. Hirman is responsible for monitoring the large solar flares -- XTC sudden bursts of energy released by sunspots during periods of high activity -- and trying to forecast the effects those solar flares can have on Earth.
The sun's 11-year cycle has a "summer and winter," Mr. Hirman said, and the sun is now in the summer phase, the most active, when storms are most likely to occur.
The center in Boulder, part of the National Oceanic and Atmospheric Administration, measures the number of sunspots with radiotelescopes and space telescopes and measures the intensity of the flares.
The last large flare occurred Wednesday evening, and its effects were reaching the Earth late yesterday afternoon. The flare was so big it was immeasurable, reaching an X class (the highest category of energy) and still "so strong the sensors couldn't measure it anymore," Mr. Hirman said.
It is likely that several more large flares will shoot out from sunspots during the next week, he said.
Much of the time the sun is quiet, explained Dr. Mario H. Acuna, an astrophysicist at the National Aeronautics and Space Administration's Goddard Space Flight Center. But when it develops an active region, it resembles a pot of boiling spaghetti sauce that spits out high-energy particles into space.
The sun emits a so-called "solar wind" made up of ionized gas.
This solar wind exerts strong pressure on the Earth's magnetic field, a huge area extending into space far beyond the thin layer of atmosphere. The solar wind cannot penetrate the Earth's magnetic field, but there are two "funnels" at the north and south poles through which it can pass.
When the high-energy particles of the solar wind whip through those funnels, they reach the atmosphere. There they excite oxygen and nitrogen atoms, causing them to glow in the green, blue and gold of the aurora borealis, the "northern lights" seen in the Northern Hemisphere, Dr. Acuna explained.
The same phenomenon occurs in the Southern Hemisphere, he pointed out.
Such disruption of the Earth's magnetic field can cause large currents of energy to circulate through power lines, overwhelming transformers. The buildup of energy can either trip circuit breakers, shutting down a transformer, or destroy it, the scientist said.
NOAA alerts utility companies when the sun shows large solar flares. But John Ponder, an engineer and solar magnetic expert at Pennsylvania, New Jersey and Maryland Inter Connection, a consortium of electrical utilities capable of sharing power, said that the government's "forecasting accuracy is very poor."
"Eighty percent of [solar] storms are not forecast," he said.
Therefore, the utilities rely on their own 24-hour monitoring to spot trouble and then try to prevent power blackouts or shortages by redistributing the electrical energy flow around trouble spots, said T. Robert Woodward, manager of the utility consortium in Valley Forge, Pa.