Solar flares can have a massive impact on global positioning system (GPS) and other technologies that use radio waves for communications. 

This conclusion comes after an unprecedented solar eruption last December, which impacted on these systems, according to researchers at Cornell University.
The findings were announced yesterday at the first Space Weather Enterprise Forum, an assembly of academic, government and private sector scientists focused on examining the Earth's ever-increasing vulnerability to space weather impacts.
Solar radio bursts begin with a solar flare that injects high-energy electrons into the solar upper atmosphere. Radio waves are produced which then propagate to the Earth and cover a broad frequency range. The radio waves act as noise over these frequencies, including those used by GPS and other navigational systems which can degrade a signal.
Forecasters from the NOAA Space Environment Center in Boulder, Colo., observed two powerful solar flares on 5 and 6 December 2006. These violent eruptions originated from a large sunspot cluster.
On 6 December 2006, a solar flare created an unprecedented intense solar radio burst causing large numbers of receivers to stop tracking the GPS signal.
Using specially-designed receivers built at Cornell University as sensitive space weather monitors, scientists were able to make the first quantitative measurements of the effect of earlier solar radio bursts on GPS receivers. Extrapolations from a previous moderate event led to the prediction that larger solar radio bursts, expected during solar maximum, would disturb GPS receiver operation for some users.
"In December, we found the effect on GPS receivers were more profound and widespread than we expected," says Dr Paul Kintner, professor of electrical and computer engineering at Cornell University. "Now we are concerned more severe consequences will occur during the next solar maximum."
Dr Dale Gary, chair and professor of the physics department at New Jersey Institute of Technology, adds: "This solar radio burst occurred during the solar minimum, yet produced as much as 10 times more radio noise than the previous record. Measurements with NJIT's solar radiotelescope confirmed, at its peak, the burst produced 20 000 times more radio emission than the entire rest of the sun. This was enough to swamp GPS receivers over the entire sunlit side of Earth."
The Global GPS Network, a set of precise GPS receivers used for a variety of scientific and real-time applications, also was affected by this solar disturbance. These applications include a very high accuracy positioning service that can provide a user's position with 10cm to 20cm accuracy anywhere in the world, on land, in the air or in Earth's orbit.
Dr Anthea Coster, from the MIT Haystack Observatory, explains that there are three key points to remember about solar radio bursts.
"First, society cannot become overly reliant on technology without an awareness and understanding of the effects of future space weather disruptions," she says.
Second, the 6 December event dramatically shows the effect of solar radio bursts is global and instantaneous.
"Third, and equally important, the size and timing of this burst were completely unexpected and the largest ever detected. We do not know how often we can expect solar radio bursts of this size or even larger."