The strength of the Earth.s magnetic field varies from place to place on the Earth.s surface.
The value of magnetic field being of the order of `10^(-5)` T.
It was believed that the magnetic field arising from a giant bar magnet placed along the axis of rotation of the Earth and deep in the interior, but this is not the truth.
The magnetic field is now thought to arise due to electric currents produced by convective motion of metallic fluids (consisting mostly of molten iron and nickel) in outer core of the Earth. This is known as the dynamo effect.
Earth.s magnetic lines are like magnetic lines of bar magnet.
The axis of the dipole does not coincides with the axis of rotation of the Earth but is presently tilted by 11.3°.
The magnetic poles are located where the magnetic field lines due to the dipole enter or leave the earth.
The location of the north magnetic pole is at a latitude of 79.74° Nanda longitude of 71.8° W, a place somewhere in north Canada. The magnetic south pole is at 79.74° S, 108.22° E in the Antarctica.
The pole near the geographic north pole of the Earth is called the north magnetic pole. Likewise the pole near the geographic south pole is called the south magnetic pole.
There is some confusion in the nomenclature of the poles. As shown figure, the magnetic field lines of Earth, one sees that unlike in the case of a bar magnet.
(1) The field lines go into the Earth at the north magnetic pole `N_m` and
(2) Come out .from the south magnetic pole `S_m`.
The convention arose because the magnetic north pole was the direction to which the north pole of a magnet needle pointed, the north pole of a magnet was so named as it was the north seeking pole. Thus, in reality, the north magnetic pole behaves like the south pole of a bar magnet inside the earth and viceversa.
