http://www.newscientisttech.com/chan...e-for-gps.html
Solar storms spell trouble for GPS

SOLAR flares can drown out GPS signals with potentially serious
consequences for airlines, emergency services, and anyone relying on
satellite navigation.

It turns out these bursts of charged particles, which produce auroras
and geomagnetic storms, also generate radio waves in the 1.2 and
1.6-gigahertz bands used by GPS.

How was such a clash missed? Because GPS receivers only became common
during a period of low solar activity. By 2011 solar flares will reach
the peak of their cycle and receivers will likely fail. Or so
Alessandro Cerruti of Cornell University, New York, told a meeting of
the Institute of Navigation in Fort Worth, Texas, last week. The only
solution would be to redesign GPS receivers or satellites, which may
not be practical, says Cerruti.

From issue 2572 of New Scientist magazine, 07 October 2006, page 27