The Earth's Magnetic Field

The force fields, what nature created long ago -- namely the protective magnetic shield, fueled by
mysterious processes deep within, that envelopes our planet. We knew nearly as little about the source
of the force fields generated by fictional starships as we did about the natural one. In space, on the
Sun and in the Earth's core, electric currents are the only source of magnetism.

 

Earth, the giant magnet

Magnetic energy generated in the Earth's core results in a geomagnetic field. This that makes compass navigation possible, also deflects and absorbs harmful solar radiation. Earth's solid inner core, mostly iron,
is surrounded by a chiefly fluid outer core, consisting mostly of molten iron. The interaction of these
two regions, in which material flows at different rates, creates what scientists call a
"hydromagnetic dynamo," something like an electric motor that results
in a magnetic field akin to a giant bar magnet.


 

Invisible geomagnetic lines stretch from one pole, curve far out into space, then back to the opposing pole. In a static environment, the curved lines might appear like a wire-frame model of some giant pumpkin, but the electrically charged solar wind blows the pumpkin into a teardrop shape. This protective field has existed in various forms for at least 3 billion years, periodically growing stronger and weaker, shifting around and, on a few occasions, even flipping its polarity entirely.


Forces of change

The planet continually regenerates its invisible, protective magnetic shield. The Earth's mantle plays a role in fueling the magnetism. How the magnetic north and south poles might migrate and, over time, even trade places. How all this erratic behavior occurs is not well understood. But radical changes seem to take place in as little as a thousand year's time, while periods of relative stability appear to reign for another 200,000 years or so. If something did not continually regenerate the magnetic field, it would degenerate to zero and our planet would be left naked, exposed to the hideous power of solar radiation.


 

The mantle, the next layer up, can also play a role. Where the core and the mantle meet, varying rates of heat exchange might create changes in the magnetic field. While much about Earth's magnetism remains a mystery, complete reversals of polarity -- and the slightly less dramatic excursions, or wanderings are among the most intriguing of terrestrial puzzles. The current results show how the temperature patterns on the lower mantle above the core, can either increase or decrease the probability of magnetic reversals.




Earth's magnetosphere




 

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