

Quiz 7  Earth as a Magnet
The Earth's magnetic field can be represented by a magnetic
dipole located at the Earth's center. The dipole model of the Earth is quite
good up to 4R_{E}, where R_{E} is the radius of the Earth.
(a) Write down the expression for the Earth's magnetic field
in spherical coordinate system assuming that the Earth's dipole moment M is
oriented along the z axis (i.e. we are working with geomagnetic coordinates).
(b) The Earth's magnetic field on the surface of the Earth
at the equator is ≈ 0.31 G. Calculate the magnetic field (magnitude and
direction) at the north and south magnetic poles. (1 G = 10^{4} T).
(c) Calculate the magnitude of the dipole moment of the
Earth. Assume the radius of the Earth to be 6000km.
Solution:
Physics key words: spherical magnetic, dipole, moment, field, radii, poles, field lines, EM, prorogation.
