Waves of charged particles thrown off by the sun have caused renewed disturbances in Earth's magnetic field in recent days, disrupting radio communications and apparently disabling power transmission equipment in Virginia. At midday Wednesday, a new wave of the particles hit the magnetic field, indicating that "we're beginning a very disturbed period," said David Speich, a scientist at the Space Environment Laboratory of the National Oceanic and Atmospheric Administration in Boulder, Colo. His agency predicted that as a result the Northern Lights could be visible as far south as Tulsa, Okla.
A round of disturbances, which scientists call geomagnetic storms, began June 4, in response to a disturbance on the sun three days earlier. Solar flares have sent waves of protons and electrons toward Earth, literally pushing the planet's magnetic field. When the field moves through Earth's crust, it generates electric currents, which can jump into power lines and disrupt transmission equipment.
The Virginia Electric and Power Co. said three capacitor banks failed simultaneously Monday. The capacitors are used to maintain voltage on transmission lines.
"It didn't present any extraordinary problems to us," said Larry W. Ellis, senior vice president of the power company, because the demand for power was not at peak.
If a geomagnetic storm caused transmission to fail at a time when the system was fully loaded, some experts say a widescale blackout could result.
The particles also disrupt the ionosphere, a layer of charged particles. In some kinds of radio transmissions, the ionosphere is used to bounce the signals back toward Earth.
In addition, the particles can deliver a radiation dose to passengers on airplanes on trans-polar flights, including most flights from the United States to Europe.
As the solar storm deforms the magnetic field, it increases the size of the polar region _ the effect that makes the Northern Lights visible so far south. The particles are drawn to the polar region and, interacting with molecules of the atmosphere or aircraft, can shake loose neutrons, which then irradiate people.