Current Distribution Models for the Earth's Main Magnetic Field: A   Discrete Inverse Theory Approach
  Current source models for the Earth's main geomagnetic field are calculated employing conventional discrete inverse theory methods. Source structures are spherical surfaces placed at the surface of the Earth's core, and at the surface of the Earth. The data set consists of measurements taken by the MAGSAT satellite in 1979. The resulting current distributions are discussed in relation to dipole and current loop models. 
Terence V. Sewards