The fact that there is the compass effect suggests that it is in some way involved with the Earth's magnetic field that protects us from the solar wind (composed of positive and negative ions). According to recent studies it appears that the effects of this wind reach down to the ground. It could be a ground battery formed around the buried metal that disturbs the ionic wind. This also explains the fact that the maximum sensitivity of Lrls is in the north / south direction if we are north of the equator instead is in the south / north if we are south of the equator. This is due to the fact that negative ions are attracted to the north pole and the south pole positive ones (or is it the other way, but it does not change).
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