Earth's magnetic field, illustration. This magnetic field (blue lines and blue circles) is generated by eddies (red circles) in the liquid core (centre), which in turn are caused by the rotation of the Earth (red circle at top). The core is about 3488 kilometres in radius. The outer core (yellow-orange) is a liquid layer of iron and nickel, extending downwards for 2210 kilometres. The inner core (centre) is a solid sphere of iron-nickel alloy, with a radius of around 1278 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.