The earth's magnetic field, with a magnetic dipole moment of 8.0×1022A?m2 , is generated by currents within the molten iron of the earth's outer core. (The inner core is solid iron.) As a simple model, consider the outer core to be a current loop made of a 1200-km-diameter "wire" of molten iron. The loop diameter, measured between the centers of the "wires", is 3070km .
What is the current in the current loop?