Laboratory analogue modelling of the Schumann Resonance source field

An oscillating vertical line current source was used in the laboratory to simulate the naturally occurring 8 Hz Schumann Resonance field due to lightning strokes. Vertical to horizontal magnetic field ratios (coast effect), and magnetotelluric ratios, for traverses over a laboratory model of the Assistance Bay region of Cornwallis Island (N.W.T. Canada) for the vertical line current source field are compared with those for an overhead uniform source field. The E- and H-polarizations of the source fields used are defined as the cases of the horizontal magnetic field of the source roughly perpendicular and parallel to the general coastline, respectively.The magnetic field ratios are essentially identical for the two field sources for E-polarization, but differ by a factor of approximately two for H-polarization, with the ratios greater for the overhead source than for the vertical line current source. The magnetotelluric ratios are found to be identical for the two field sources of each of the E- and H-polarizations.