It is a theory that explains the origin of the Earth's main magnetism in terms of a self-sustaining dynamo.
In this dynamo mechanism, fluid motion in the Earth's outer core moves conducting material (liquid iron) across an already existing, weak magnetic field and generates an electric current.
The electric current, in turn, produces a magnetic field that also interacts with the fluid motion to create a secondary magnetic field.
Together, the two fields are stronger than the original and lie essentially along the axis of the Earth's rotation.
The Doppler Effect:
The Doppler effect is the change in frequency of a wave with respect to an observer who is moving relative to the wave source.
The changing pitch of the train siren is the best example of the Doppler effect.
The Magnus effect:
The Magnus effect is related to the spinning bodies (either cylinder or sphere)
When a soccer player kicks a ball off-centre it causes the ball to spin due to the Magnus effect.