Solar Flares Could Disable Mobile Phones

Solar flares could knock out GPS enabled mobile phones, reports researchers at Cornell University. Because solar flares -- larger-than-normal radiation "burps" by the sun -- are generally unpredictable, such failures could be devastating for "safety-of-life" GPS operations -- such as navigating passenger jets, stabilizing floating oil rigs and locating mobile phone distress calls.

Only yesterday, we carried a report that expects a significant uptake in GPS enabled cell phones.

Solar particles interact with Earth's magnetosphere

Alessandro Cerruti, a graduate student working for Kintner, accidentally discovered the effect on Sept. 7, 2005, while operating a GPS receiver at Arecibo Observatory in Puerto Rico, one of six Cornell Scintillation Monitor (SCINTMON) receivers. Cerruti was investigating irregularities in the plasma of the Earth's ionosphere -- a phenomenon unrelated to solar flares -- when the flare occurred, causing the receiver's signal to drop significantly.

To be sure of the effect, Cerruti obtained data from other receivers operated by the Federal Aviation Administration (FAA) and the Brazilian Air Force. He found that all the receivers had suffered exactly the same degradation at the exact time of the flare regardless of the manufacturer. Furthermore, all receivers on the sunlit side of the Earth had been affected.

Cerruti will report on the findings at the Institute of Navigation Meeting, where he will receive the best student paper prize. The full results of the discovery will be published in a forthcoming issue of the journal Space Weather.

The flare consisted of two events about 40 minutes apart: The first lasted 70 seconds and caused a 40 percent signal drop; the second lasted 15 minutes and caused a 50 percent drop. But this flare was moderate and short-lived; in 2011 and 2012, during the next solar maximum, flares are expected to be 10 times as intense and last much longer, causing signal drops of over 90 percent for several hours.

The only solutions, suggested Kintner, are to equip receivers with weak signal-tracking algorithms or to increase the signal power from the satellites. Unfortunately, the former requires additional compromises to receiver design, and the latter requires a new satellite design that neither exists nor is planned.

"I think the best remedy is to be aware of the problem and operate GPS systems with the knowledge that they may fail during a solar flare," Kintner said.

The team was initially confused as to why the flare had caused the signal loss. Then Kintner recalled that solar flares are accompanied by solar radio bursts. Because the bursts occur over the same frequency bands at which GPS satellites transmit, receivers can become confused, leading to a loss of signal."

Posted to the site on 29th September 2006