At the Earth's magnetic pole in the northern hemisphere, the magnetic field has a strength of 0.6 G and points down toward the center of the Earth. You deduce that the Earth's magnetic field must be produced by a current loop deep inside the Earth! You guess that the radius of the loop is about 1300 km (the radius of the liquid metal layer known as the outer core). (a) How much current must it carry? (b) Does the current flow the same way as the Earth's rotation, or opposite? [Hints: use results we have derived in class for the field on the axis of a current loop] R1 P Ir 1 Geomagnetic field upper mantle ubducting slab outer core plume head inner core plume tail slab remnant lower mantle continent orogeny continent LLSVP crust