**3. A long wire on the surface of a conductive half space**

A single wire grounded at both ends and connected to an alternating current (AC) generator will set up an alternating magnetic field (primary field), which will induce a voltage in the ground. This will in turn produce inductive currents in the

*Long Wire Electromagnetic Measurements (Turam EM) DOI: http://dx.doi.org/10.5772/intechopen.91387*

**Figure 2.** *Secondary magnetic field from induced currents in a conducting half-space [6].*

conductive half-space with its own magnetic field (secondary field). This secondary magnetic field is opposing the primary field in the ground, thus weakening the magnetic field from the wire. The resulting field will not penetrate as deep into the ground as in free space and will be phase-shifted relative to the primary field. **Figure 1** shows the resultant field calculated for a two-dimensional model of the half-space and a conductor [6].

The secondary magnetic field alone can be computed and displayed. **Figure 2** shows the induced magnetic field from currents in a conducting half-space without conductor [6]. The induced currents in the ground create a circular pattern of the magnetic field with the vortex below the cable. The depth of the vortex is approximately half the skin depth.
