Symbol of Infinity
Earth's surface and its inhabitants are protected from dangerous cosmic
radiation (energetic protons) from the Sun by the Earth's magnetic field.
Using the right hand rule one can see that positively charged particles
coming from the Sun will be deflected in east direction.
Magnetic fields are produced by the motion of electrical charges. For
example, the magnetic field of a bar magnet results from the motion
of negatively charged electrons in the magnet. The origin of the Earth's
magnetic field is not completely understood but is thought to be associated
with electrical currents produced by the coupling of convective effects
and rotation in the spinning liquid metallic outer core of iron and
nickel. This mechanism is termed the dynamo effect.
Rocks that are formed from the molten state contain indicators of the
magnetic field at the time of their solidification. The study of such
"magnetic fossils" indicates that the Earth's magnetic field
reverses itself every million years or so (the north and south magnetic
poles switch). This is but one detail of the magnetic field that is
not well understood.
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.
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.
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.