Our planet s magnetic field is believed to be generated deep down in the Earth s core. Nobody has ever taken the mythical journey to the centre of the Earth, but by studying the way shockwaves from earthquakes travel through the planet, physicists have been able to work out its likely structure. Right at the heart of the Earth is a solid inner core, two thirds of the size of the Moon and composed primarily of iron. At a hellish 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, a 2,000 km thick layer of iron, nickel, and small quantities of other metals.
Lower pressure than the inner core means the metal here is fluid. Differences in temperature, pressure and composition within the outer core cause convection currents in the molten metal as cool, dense matter sinks whilst warm, less dense matter rises. The Coriolis force, resulting from the Earth s spin, also causes swirling whirlpools. This flow of liquid iron generates electric currents, which in turn produce 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 that separate magnetic fields created are roughly aligned in the same direction, their combined effect adding up to produce one vast magnetic field engulfing the planet.
Asked by Andy Barret Planetary magnetic fields are produced by churning motions of liquids at a planetБs core that conduct electricity and have an electric charge. The magnetic fields act like giant bar magnets and can be offset from the rotation axis of a planet. For example, the EarthБs magnetic field is tilted about 11 degrees to the axis of rotation. Magnetic fields protect a planet from the charged particles streaming out from the Sun in the form of the solar wind.
The particles are deflected outwards by the magnetic field lines. Earth has a strong magnetic field because it has a liquid conducting core composed of iron-nickel that rotates swiftly every 24 hours. In contrast, Mars exhibits only remnants of an ancient magnetic field because the iron core has cooled for unknown reasons and perhaps solidified. Keep up to date with theб latestб news in All About Space Б availableб everyб monthб for just бе4. 99. Get 5 issues of All About Space for just бе5 with our latestб! б Tags:,