Study: Earth's Magnetic Field is Changing

[sharon sanders]

Study: Earth's magnetic field is changing

Observing fluid motions in core could help scientists predict future changes

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By Jeremy Hsu

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Something beneath the surface is changing Earth's protective magnetic field, which may leave satellites and other space assets vulnerable to high-energy radiation.

The gradual weakening of the overall magnetic field can take hundreds and even thousands of years. But smaller, more rapid fluctuations within months may leave satellites unprotected and catch scientists off guard, new research finds.

A new model uses satellite data from the past nine years to show how sudden fluid motions within the Earth's core can alter the magnetic envelope around our planet. This represents the first time that researchers have been able to detect such rapid magnetic field changes taking place over just a few months.

"There are these changes in the South Atlantic, an area where the magnetic field has the smallest envelope at one third [of what is] normal," said Mioara Mandea, a geophysicist at the GFZ German Research Center for Geosciences in Potsdam, Germany.Even before the newly detected changes, the South Atlantic Anomaly represented a weak spot in the magnetic field — a dent in Earth's protective bubble.


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http://www.msnbc.msn.com/id/26273268/

 

[Ronan Kelly]

Re: Study: Earth's Magnetic Field is Changing

Courtesy of the British Geological Survey;

A magnetic reversal in progress?
The South Atlantic Anomaly (SAA) is known to be growing in extent and spreading westwards from South Africa, as the Earth?s internal magnetic field rapidly weakens in this region. This may be early evidence of a forthcoming reversal in the direction of the Earth?s internal magnetic field. We do not know in detail precisely what occurs during such reversals, including the changes observed in the magnetic field and the time a reversal takes to complete. However these factors are important in knowing where the radiation risk may be increased and how the atmosphere might respond.

Earth?s magnetic field has had many highs, lows and reversals in its past. The last reversal was around 800,000 years ago. So the Earth is known to be able to re-generate its field and has done so during human pre-history. Understanding the development of the SAA may therefore be significant in understanding the reversal process and its impact on life and the natural environment

What is the South Atlantic Anomaly?
The Earth?s magnetic field, generated deep within the planet, is a shield against particle radiation from space. In the South Atlantic this shield is much weaker than elsewhere across the globe and radiation from space therefore penetrates deeper into the atmosphere. This region is known as the South Atlantic Anomaly (SAA) and the radiation in the SAA is a known hazard to satellites, spacecraft and high-altitude aircraft.

Monitoring changes in magnetic field
The radiation input into the atmosphere depends on the Sun?s magnetic and radiation activity and the geometry (or ?shape?) of the Earth?s magnetic field. So, understanding the space environment, particularly during magnetic storms, is important. Equally important is understanding any changes over time in the magnetic field observed across the surface of the Earth ? see also Long-term monitoring of the Earth?s magnetic field.

http://www.bgs.ac.uk/research/highlights/southAtlantic2010.html

Is there any danger to life?
Almost certainly not. The Earth's magnetic field is contained within a region of space, known as the magnetosphere, by the action of the solar wind. The magnetosphere deflects many, but not all, of the high-energy particles that flow from the Sun in the solar wind and from other sources in the galaxy. Sometimes the Sun is particularly active, for example when there are many sunspots, and it may send clouds of high-energy particles in the direction of the Earth. During such solar 'flares' and 'coronal mass ejections', astronauts in Earth orbit may need extra shelter to avoid higher doses of radiation. Therefore we know that the Earth's magnetic field offers only some, rather than complete, resistance to particle radiation from space. Indeed high-energy particles can actually be accelerated within the magnetosphere.

At the Earth's surface, the atmosphere acts as an extra blanket to stop all but the most energetic of the solar and galactic radiation. In the absence of a magnetic field, the atmosphere would still stop most of the radiation. Indeed the atmosphere shields us from high-energy radiation as effectively as a concrete layer some 13 feet thick.

Human beings have been on the Earth for a number of million years, during which there have been many reversals, and there is no obvious correlation between human development and reversals. Similarly, reversal patterns do not match patterns in species extinction during geological history.

Some animals, such as pigeons and whales, may use the Earth's magnetic field for direction finding. Assuming that a reversal takes a number of thousand years, that is, over many generations of each species, each animal may well adapt to the changing magnetic environment, or develop different methods of navigation.

http://www.geomag.bgs.ac.uk/education/reversals.html