 While the inner core is a solid metallic core, only 760 miles in diameter, hard to believe, as hot as the temperature of the surface of the sun. While the whole outer core spins to create our magnetic field, as I mentioned, but some now say, through seismic wave activity in the Earth, the inner core may have stopped spinning and reversed direction. If so, there may be a 60 to 70 year cycle in all this, but not to panic, as much more needs to be investigated about our home planet Earth.