Explanation

(b) Earth’s field is the effect of complex convention currents in the magma, which must be described as several dipoles, each with a different intensity and orientation, the compass actually point to the sum of the effects of these dipoles. In other words, it aligns itself with the magnetic lines of force. Other factors, of local and solar origin, further complicate the resulting field. It may be all right to say that a compass needle points ”magnetic north” but it only roughly points to the north magnetic dipole. Hence, at the magnetic poles of the earth, a compass needle will be bent slightly.