February 3, 2019
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How does a liquid iron core create Earth’s magnetic field?
Our planet's magnetic field is believed to be generated deep down in the Earth's core. Nobody has ever journeyed to the centre of the Earth, but by studying shockwaves from earthquakes, physicists have been able to work out its likely structure.
At the heart of the Earth is a solid inner core, two thirds of the size of the moon, made mainly of iron. At 5,700°C, this iron is as hot as the Sun's surface, but the crushing pressure caused by gravity prevents it from becoming liquid.
Surrounding this is the outer core there is a 2,000 km thick layer of iron, nickel, and small quantities of other metals. The metal here is fluid, because of the lower pressure than the inner core.
Differences in temperature, pressure and composition in the outer core cause convection currents in the molten metal as cool, dense matter sinks and warm matter rises.
The 'Coriolis' force, caused by the Earth's spin, also causes swirling whirlpools. This flow of liquid iron generates electric currents, which in turn create magnetic fields.
Charged metals passing through these fields go on to create electric currents of their own, and so the cycle continues. This self-sustaining loop is known as the geodynamo.
The spiralling caused by the Coriolis force means the separate magnetic fields are roughly aligned in the same direction, their combined effect adding up to produce one vast magnetic field engulfing the planet.
Extracted from: www.dailymail.co.uk
