Electronics – Solar flares


Solar flares could leave you withouta functioning GPS

Solar flares could leave you withouta functioningGPS

Boat owners using GPS — and who doesn’t? — might want to brush up on their traditional navigation skills as we approach a heightened period of solar weather that can weaken and even knock out GPS signals.

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“This is a wake-up call,” says Bob Sweet, a nationally known navigation expert and author of “The Weekend Navigator” and several other books on marine electronics. “You need to have your paper charts at the helm and make sure your dead-reckoning skills are up to the task.”

Two powerful solar flares in December 2006 have heightened concerns about the susceptibility of GPS to solar-weather phenomena. A solar flare Dec. 6 led to a solar burst that interrupted nearly all GPS transmissions on the lighted side of the earth, according to scientists with CornellUniversity in Ithaca, N.Y. Some transmissions lost strength and accuracy, while others were completely cut off for 10 minutes or longer. (A solar flare on the previous day did not lead to a solar burst.)

Solar activity is cyclical, reaching its most active period toward the end of an 11-year cycle. The current solar cycle maxes out in 2011. What’s alarming to scientists is that the Dec. 6 burst occurred in a “solar minimum” period of less activity.

“In December [2006] we found the effects on GPS receivers were more profound and widespread than we expected,” says Paul Kintner, Ph.D., professor of electrical and computer engineering at Cornell. “Now we are concerned more severe consequences will occur during the next solar maximum.”

Solar bursts start when a solar flare injects high-energy electrons into the solar upper atmosphere, producing a broad frequency range of radio waves that travel to the earth, according to scientists and the government. The radio waves act as noise over these frequencies, including those used by GPS and other navigational systems, which can degrade a signal, they say.

A large sunspot cluster caused the two solar flares in December. Several universities — including Cornell, BostonCollege and the Massachusetts Institute of Technology — and the National Oceanic and Atmospheric Administration were involved in tracking and assessing the flares. “The size and timing of this burst were completely unexpected and the largest ever detected,” says Anthea Coster, Ph.D., with MIT’s Haystack Observatory. “We do not know how often we can expect solar radio bursts of this size or even larger.”

The Dec. 6 event was so strong that researchers learned that even WAAS-enabled GPS can be affected, although not as severely as non-WAAS receivers. All of this, Sweet says, illustrates the need for boaters to reacquaint themselves with their paper charts and traditional navigation practices and tools — parallel rules, dividers, protractors and the like.

“We’ve gone through [solar activity] peaks before,” says Sweet. “But remember that many more people are using GPS than during the last peak [2000] — and using it more frequently.”

Some GPS units will alert the user that the signal has been lost and transition into dead-reckoning mode, says Sweet. In this mode, the GPS indicates the last known position.

“You always want to know where you are on the water,” says Sweet. “You’re in good shape if you can point to your current position on the chart within 10 seconds.”