Earth's magnetic field, computer artwork. The magnetic poles are shown as yellow lines. Magnetic field lines (orange) can be seen emerging from the south magnetic pole and converging at the north magnetic pole, which is offset from the geographic north pole (blue lines) by 11 degrees. The field, which closely resembles that of a bar magnet, is thought to be generated by the dynamo effect. Inside the Earth's outer core, convection heating causes cells of ionised metal to rise and fall in a circular motion (orange circles). These act like gigantic electrical currents, which in turn generate the magnetic field.