Geophysicist from University of California, Berkeley, has made the first-ever measurement of the magnetic strength of the inside Earth's core, 1,800 miles underground.
They found out the the magnetic field strength is 25 Gauss(50x stronger than the magnetic field at the surface that makes compass needles align north-south).
This was published in the Dec. 16 issue of the journal Nature.
Most of the Earth's magnetic field is produced in the outer two-thirds of the planet's iron/nickel core which thickness is about 1,400 miles and is liquid state, while the inner core is a frozen iron and nickel wrecking ball with a radius of about 800 miles(approx the size of the moon).
Researchers noted that the calculated field 25 Gauss – is an average over the entire outer core. The field is expected to vary with position.
Src: [University of California - Berkeley]