Can’t stand the heat

If heat destroys magnetism, why doesn’t the heat inside Earth destroy its magnetic field?

■  Magnetic fields are generated by the movement of electrical charges in a process called electromagnetic induction. A single electron orbiting the nucleus of an atom generates  only a weak magnetic dipole.  For a piece of solid material to  be a permanent magnet on a macro-scale, the dipoles need  to align, which is what happens  in materials like iron and nickel. However, when the material is heated above a certain temperature, the Curie temperature, thermal vibration of the atoms starts to push the dipoles out of alignment, and the material loses its bulk magnetism. So heat does not destroy magnetism; it merely disrupts  the alignment of the dipoles such that, at a macro-scale, there is no longer any net magnetic field. Earth’s magnetic field is believed to be generated by electric currents in its molten core, which is mainly iron. These electric currents are formed  by convection currents of radioactive heat escaping from the core. If the core was not hot enough to be liquid, no flow would occur and no magnetic field would be induced. A similar process occurs in the sun to produce its magnetic field. Simon Iveson Chemical Engineering Discipline University of Newcastle New South Wales, Australia