The Pilgrim's Journey
"Understanding just how Earth's magnetic field responds to such events is now a focus of much solar and space research. We are increasingly dependent on technologies that are extremely sensitive to changes in the space environment, changes often collectively referred to as "space weather."...
Transient events on the Sun can generate fast-moving clouds of particles that greatly intensify the solar wind's impact on Earth. Solar flares may blast material from the Sun's surface for hours. Areas called coronal holes generate broad torrents of solar wind and may last for many months. But the most dramatic space-weather effects arise when enormous clouds of material erupt from the solar atmosphere and race to Earth. Scientists call these eruptions coronal mass ejections, or CMEs. Somehow, a portion of the Sun's magnetic field undergoes a sudden disruption, stretching and twisting like a rubber band until it snaps. When it does, as much as one billion tons of matter blast away from the Sun at speeds up to 1,250 miles (2,000 km) a second. When a CME slams into Earth's magnetic bubble, it pushes the sunward side closer to Earth and triggers other sudden changes. The result is a surge of particles into Earth's atmosphere a geomagnetic storm."
An extremly large aurora occurred on March 14, 1989. The Dynamics Explorer 1 satellite captured an image of the auroral oval over Earth's south polar regions. Scientists then remapped the image along magnetic field lines to show what the northern auroral oval (top) would have looked like at the same time. NASA / GSFC / Univ. of Iowa [larger image]
The atmospheric activity responsible for the northern lights occasionally has a profound effect on everyday life. "During the aurora of September 2, 1859," wrote American researcher Elias Loomis (1811-1889), "the currents of electricity on the telegraph wires were so steady and powerful that, on several lines, the operators succeeded in using them for telegraphic purposes as a substitute for the battery." For a time, messages were transmitted solely on auroral currents.
A rapidly shifting and expanding auroral oval can induce electrical currents in other long conductors as well. An example that has become legend in the space-weather community occurred in March 1989, when an extremely active solar region broke records held for more than 30 years: Auroral activity was seen as far south as Jamaica. In Quebec, Canada, aurora-induced currents flowed through seven 100-ton capacitors operated by the Hydro-Quebec Power Authority, causing their protective relays to detect an overload condition. When the relays kicked in and took the devices off-line, about half of Quebec's available electrical power went with them. Less than one minute later, the entire power-distribution system collapsed, leaving some 6 million people without electricity for more than 9 hours.