The magnetic field of the Earth is roughly that of a magnetic dipole located at the centre of the Earth. At 15 Earth radii from the centre, the magnitude of B in the equatorial plane is found to be 10 nano Tesla.
What is the magnetic dipole moment of the Earth? (Radius of Earth ~ 6000km)
b) If the Earth's dipole moment were attributed to an electric current circulating in the core at effectively one third radius from the centre, how large would this current be?