Electromagnetic inverse problems with surface measurements at low frequencies

This paper deals with the following inverse problem. A time-harmonic magnetic dipole is moved along the surface of the Earth; inside the Earth there is a bounded regular region of inhomogeneity where the electromagnetic parameters in , mu and sigma (permittivity, permeability and conductivity) vary; outside this region they are assumed to be constants. The scattered electric or magnetic field is then measured everywhere on the surface of the Earth with low transmitter frequencies. The problem is to find the parameters describing the inhomogeneity from these measurements. An exact analytic inversion formula is given in the special case when mu and sigma are positive constants and in is allowed to vary. The general case is treated in this work approximately by using a version of the Born inversion.