WASHINGTON - A magnetic storm that could disrupt radio transmissions and satellites - and also produce colorful northern lights - is expected to strike the earth Saturday and could last until Monday.
The massive sunspot eruption took place early Friday, the National Oceanic and Atmospheric Administration reported.
''The storm is expected to reach strong to severe levels, which can adversely affect satellite operations and power grids,'' reported the agency.
In addition, space weather forecasters said there is a good chance of seeing the Aurora Saturday through Sunday morning in cities as far south as Washington, D.C., Seattle, New York and Denver.
NOAA's Space Environment Center in Boulder, Colo., reported that Friday's large complex sunspot group produced one of the largest solar flares seen in recent years.
The solar flare, a giant eruption bursting out from the surface of the sun, took place about 6:24 a.m. EDT, the center said.
The event ejected billions of tons of plasma and charged particles into space, some of it heading toward Earth at 3 million miles per hour. The mass ejection is expected to strike the Earth's magnetic field on Saturday afternoon and cause the geomagnetic storm.
The Earth's magnetic field protects the planet from most such charged particles, but in a strong burst such as this some disruptions can occur. As the field deflects the incoming particles they are moved toward the north and south poles where they cause the northern and southern lights, called auroras.
The NOAA scientists reported that the solar flare has already caused some effects on Earth, including some radio blackouts.
A NASA satellite located about one million miles upstream from Earth detects geomagnetic storms approaching Earth and provides NOAA forecasters with a warning about one hour before they reach Earth's magnetic field.
In 1989, a severe solar storm knocked out power stations serving Canada and the northeastern states, as well as an electrical transformer in New Jersey. Since then, power grid and satellite operators have taken steps to protect their systems.
The sun is currently in the most intense phase of its 11-year sunspot cycle.
On the Net:
NOAA Space Environment Center: www.sec.noaa.gov