Earth's interior and magnetic field. Illustration of the internal structure of the Earth, showing the magnetic field (white lines) generated by the eddies (blue spirals) set up in the liquid core. The mantle (solid and semi-molten rock, orange) extends downwards for 2855 kilometres from below the crust. The core has a radius of 3488 kilometres. The Earth's magnetic field extends outwards into space for tens of thousands of kilometres, protecting the planet from high-energy radiation from the Sun.