[National Geographic] ~ As Sun Storms Ramp Up, Electric Grid Braces for Impact
Storms are brewing about 93 million miles (150 million kilometers) away, and if one of them reaches Earth, it could knock out communications, scramble GPS, and leave thousands without power for weeks to months.
The tempest is what's known as a solar storm, a flurry of charged particles that erupts from the sun. Under the right conditions, solar storms can create extra electrical currents in Earth's magnetosphere—the region around the planet controlled by our magnetic field.
The electrical power grid is particularly vulnerable to these extra currents, which can infiltrate high-voltage transmission lines, causing transformers to overheat and possibly burn out."