Chances are you probably missed last week's appearance of Sunspot No. 10,981 on the surface of the sun.
But scientists say its arrival signals the beginning of a cycle of solar storms that could make everything from your cell phone to the GPS navigation system in your car temporarily stop working. And in severe storms, experts say it's possible entire power grids could be knocked out, leaving millions in the dark.
Sunspots are areas of intense magnetic activity on the sun that appear on roughly an 11-year cycle. The location and characteristics of Sunspot No. 10,981 tell scientists that the newest cycle -- known as Solar Cycle 24 -- has begun. The solar activity can release tremendous blasts of energy toward Earth -- interfering with an array of sensitive electronic systems.
Experts say the periods of solar storm activity should gradually increase, peaking by the year 2011 or 2012.
Dale Gary, a solar physicist who chairs the physics department at the New Jersey Institute of Technology, says cell phone towers will likely bear the brunt of a solar storm.
"It can affect quite a number of towers in a given region," said Gary, who notes one study he conducted showed a typical storm could affect about 7 percent of all cell phone calls. A stronger storm could make the problem worse.
Of particular concern, experts say, is the effect solar storms could have on GPS navigation devices that have come into much wider civilian use in the last five years.
The system relies on Earth-orbiting satellites to provide precise locations anywhere on the planet. But solar storms could make GPS receivers unable to lock onto a satellite signal, rendering them useless. The effect could last for minutes or more than a day. You may be reduced to -- gasp -- stopping to ask for directions.
"The civilian use of GPS has really taken off only in the last few years, so we really do expect to see a much wider impact in this upcoming cycle," said Douglas Biesecker, a solar physicist at the Space Weather Prediction Center in Colorado, run by the National Oceanic and Atmospheric Administration.
Sales of so-called personal navigation devices -- those manufactured by companies like Magellan and Garmin, for example -- have skyrocketed in recent years. In 2004, worldwide sales of GPS units were about 2 million. By 2007, that number had jumped to about 27 million, according to technology analysts at ABI Research.
"It's difficult to find a product with similar growth rates," said ABI principal analyst Dominique Bonte. He predicted that by 2011, when the storms are expected to peak, worldwide GPS sales will hit 100 million devices annually.
The impact on GPS units could be especially serious for pilots, farmers and surveyors -- anyone who needs precision accuracy, says Biesecker.
"Imagine if you're laying a highway," he said. "You pave, and then have to rip it up and start it all over again. It's happened."
And scientists say there's not much to be done except wait out the storm with a potentially huge economic impact across industries.
"If you are doing precision GPS, where you need centimeter activity, you basically have to cease operations until the event is over," Gary said.
Another serious impact could be on power transmission lines, which are susceptible to bombardment by electrical interference. A 1989 solar storm, for example, knocked out power to 6 million people in Canada's Quebec Province. Power utilities in New Jersey and other U.S. states were also affected.
Solar storms that hit Earth in the fall of 2003 had wide-ranging impacts, from blackouts in Sweden to the loss of a $640 million science satellite, according to a NOAA report. Airlines also had to reroute flights over high latitudes because of communications blackouts and high levels of radiation exposure -- at a cost of $10,000 to $100,000 per flight, the report said.