Irregularities in Earth's atmosphere can distort GPS signals

Scientists are studying the irregularities in Earth's upper atmosphere, that can distort GPS signals, to help overcome their effects on communications.

PTI| Updated: Mar 01, 2015, 22:25 PM IST
Irregularities in Earth's atmosphere can distort GPS signals

Washington: Scientists are studying the irregularities in Earth's upper atmosphere, that can distort GPS signals, to help overcome their effects on communications.

Signals travelling between Global Positioning System (GPS) satellites and electronic devices, especially at high latitudes, can get distorted in Earth's upper atmosphere.

Researchers at NASA's Jet Propulsion Laboratory in California, in collaboration with the University of New Brunswick in Canada, are studying irregularities in the ionosphere, a part of the atmosphere centred about 350 kilometres above the ground that defines the boundary between Earth and space.

The study compares turbulence in the auroral region to that at higher latitudes, and gains insights that could have implications for the mitigation of disturbances in the ionosphere.

Auroras are spectacular multicoloured lights in the sky that mainly occur when energetic particles driven from the magnetosphere, the protective magnetic bubble that surrounds Earth, crash into the ionosphere below it.

"We want to explore the near-Earth plasma and find out how big plasma irregularities need to be to interfere with navigation signals broadcast by GPS," said Esayas Shume, a researcher at JPL and the California Institute of Technology in Pasadena, and lead author of the study.

If you think of the ionosphere as a fluid, the irregularities comprise regions of lower density (bubbles) in the neighbourhood of high-density ionisation areas, creating the effect of clumps of more and less intense ionisation.

This "froth" can interfere with radio signals including those from GPS and aircraft, particularly at high latitudes.

The size of the irregularities in the plasma gives researchers clues about their cause, which help predict when and where they will occur. More turbulence means a bigger disturbance to radio signals.

"One of the key findings is that there are different kinds of irregularities in the auroral zone compared to the polar cap," said Anthony Mannucci, supervisor of the ionospheric and atmospheric remote sensing group at JPL.

"We found that the effects on radio signals will be different in these two locations," said Mannucci.

The researchers found that abnormalities above the Arctic polar cap are of a smaller scale - about 1 to 8 kilometres - than in the auroral region, where they are 1 to 40 kilometres in diameter.

Shume said the polar cap is connected to solar wind particles and electric fields in interplanetary space.

On the other hand, the region of auroras is connected to the energetic particles in Earth's magnetosphere, in which magnetic field lines close around Earth. These are crucial details that explain the different dynamics of the two regions.

The study was published in the journal Geophysical Research Letters.