Magnetic Field :
Earth's surface and its inhabitants are protected from dangerous
cosmic radiation (energetic protons) from the Sun by the Earth's
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.
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
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
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