‘Minor’ Magnetic Storm Is Expected From Sun Flares
Explosions last week on the sun’s surface were some of the most spectacular in recent years, but scientists say they expect their effect on Earth to be minimal.
Radioactive particles from Friday’s solar explosions have not reached Earth’s atmosphere as expected, space scientist Kent A. Doggett said Saturday, downgrading earlier predictions of a “major” magnetic storm and disruptions to communications systems, as well as dazzling aurora displays in some northern states.
“We suspect that the amount of energy released by the flares was not as great as originally thought,” said Doggett of the National Oceanic and Atmospheric Administration’s space environmental laboratory in Boulder, Colo.
2-Day Magnetic Storm
Although the radiation hurled to Earth by the explosions is still expected to create a two-day magnetic storm beginning as early as tonight, the severity of the storm has been downgraded to “minor,” Doggett said. Storms of greater intensity are not uncommon, he said, noting that one occurred as recently as last month.
Two large flares, the stronger of which lasted almost an hour and reached thousands of miles above the sun’s surface, occurred between 9 and 10 a.m. Friday, said Randy Fear, a physicist who observed the phenomenon at Caltech’s Big Bear Solar Observatory, northeast of Los Angeles.
Categorized as a rare “white flare,” the stronger explosion’s magnitude was last matched in 1984, Fear said. “We may only get half a dozen or so white flares in an 11-year solar cycle,” he said.
But why the magnetic storm will apparently fail to measure up to the intensity of the flare that created it remains a “mystery,” Doggett said. “That’s why predicting this sort of disturbance is so difficult.”
Sun flares cause explosive blasts of energy that send electrically charged particles, X-rays and light hurling into space. Protons and neutrons that enter Earth’s magnetic field strike the ionosphere, a layer of electrically charged particles that surround Earth, and alter its balance creating a magnetic storm.
Changes in Ionosphere
Radio waves usually bounce off the ionosphere and, during these short-term disturbances, changes in the ionosphere cause disruptions in radio communications, particularly short-band radio, Fear said. The storms may also disrupt satellite and commercial airliner communications, electronic surveillance of ground-based weapons system and even overload electrical transformers.
But the levels of such disruptions are expected to be minor, said Doggett.
When energetic protons stream toward Earth’s North and South Poles, striking particles in Earth’s atmosphere and becoming ionized, they glow, causing a neon-like effect called the aurora borealis. The intensity of the recent sun flares was expected to expand the effect as far south as Boston, but under the revised forecast, it is expected to be visible no farther south than southern Canada, Doggett said.
No other large flares are anticipated from the southwestern quadrant of the sun that produced Friday’s explosions, said Fear, adding that the region is about to rotate out of view from Earth.
But Fear said overall solar activity is intensifying as the sun approaches 1991, the peak year of its 11-year cycle. Sunspots signal the occurrence of flares and their number has risen at a rapid rate, signaling, perhaps, a period of unusual sun flare activity, he said.
“This could be one of the largest solar cycles ever,” he said.
