<P> The Earth's magnetic north pole is drifting from northern Canada towards Siberia with a presently accelerating rate--10 kilometres (6.2 mi) per year at the beginning of the 20th century, up to 40 kilometres (25 mi) per year in 2003, and since then has only accelerated . </P> <P> The Earth's magnetic field is believed to be generated by electric currents in the conductive material of its core, created by convection currents due to heat escaping from the core . However the process is complex, and computer models that reproduce some of its features have only been developed in the last few decades . </P> <P> The Earth and most of the planets in the Solar System, as well as the Sun and other stars, all generate magnetic fields through the motion of electrically conducting fluids . The Earth's field originates in its core . This is a region of iron alloys extending to about 3400 km (the radius of the Earth is 6370 km). It is divided into a solid inner core, with a radius of 1220 km, and a liquid outer core . The motion of the liquid in the outer core is driven by heat flow from the inner core, which is about 6,000 K (5,730 ° C; 10,340 ° F), to the core - mantle boundary, which is about 3,800 K (3,530 ° C; 6,380 ° F). The heat is generated by potential energy released by heavier materials sinking toward the core (planetary differentiation, the iron catastrophe) as well as decay of radioactive elements in the interior . The pattern of flow is organized by the rotation of the Earth and the presence of the solid inner core . </P> <P> The mechanism by which the Earth generates a magnetic field is known as a dynamo . The magnetic field is generated by a feedback loop: current loops generate magnetic fields (Ampère's circuital law); a changing magnetic field generates an electric field (Faraday's law); and the electric and magnetic fields exert a force on the charges that are flowing in currents (the Lorentz force). These effects can be combined in a partial differential equation for the magnetic field called the magnetic induction equation, </P>

Where does the force that creates a magnetic field come from