The Sun hurled a huge cloud of charged particles at Earth on Tuesday, with an intensity that could affect satellites, power grids and pipelines when it reaches our planet, possibly as soon as Wednesday.

The cloud, known to astronomers as a coronal mass ejection, is the one of the strongest ever detected since scientists started measuring these phenomena a quarter-century ago. It is vastly stronger than a series of solar flares that headed toward Earth last week.

Aside from affecting some modern electronics and navigation equipment, the solar storm could also create an aurora that might be visible as far south as the southern United States and southern Europe, said Paal Brekke, a scientist who works with the SOHO satellite that first detected the blast.

"For most people this will be a great event," Brekke said by telephone. "People on the ground shouldn't worry. The only thing you should be aware of is that some of the modern equipment -- GPS, pager, cellphone -- some of these will fail. Most of the time, we can live without them."

The monstrous solar flare erupted from a big sunspot at about 6 a.m. EST (1100 GMT) on Tuesday, sending the coronal mass ejection directly toward Earth at about 1,300 miles per second, about five times as fast as most coronal mass ejections, Brekke said.


When that cloud of particles gets here -- perhaps by midday Wednesday but the exact arrival time is unclear -- it could have severe effects, Brekke said.

"We don't know really how severe this will be until it hits the Earth or until it hits SOHO," he said. The key is to figure out the direction of the magnetic field embedded in the cloud. If the magnetic field is pointing northward, the same as the northward orientation of Earth's magnetic field, "it will glide more easily past us."

If the field is pointing southward, "it will have a very dramatic effect on the system ... it will shake up our whole magnetosphere and cause a severe geomagnetic storm."

The National Oceanographic and Atmospheric Administration said a strong geomagnetic storm like this one -- classified as a G-5, the strongest category -- could cause widespread voltage control problems in power systems, including transformer damage, could cause problems with satellites and other spacecraft and could cause charging of currents in pipelines.

Two other such solar storms have been stronger, including one that affected Canadian power grids in 1989.

Earth's magnetosphere consists of electrically charged particles which bounce around above Earth, trapped in our planet's magnetic field. When some of these particles escape into the atmosphere, they create the aurora -- aurora borealis when seen in the northern hemisphere and the aurora australis in the southern hemisphere.

For those in areas where the cloud will arrive during daylight, the aurora will not be visible. However, the midday arrival time predicted for the eastern United States could be off by six to eight hours either way, Brekke said.

Real time images of the ejection cloud are available online at http://sohowww.nascom.nasa (news - web sites).gov/data/realtime-images.html.

--Reuters