MAGNETIC SENSIBILITY. “There is evidence for robust interactions of weak extremely low frequency magnetic fields with biological systems. We suggest that the biological basis is likely to be found in the weak (∼50 nT) daily swing in the geomagnetic field that results from the solar tidal force on free electrons in the upper atmosphere, a remarkably constant effect exactly in phase with the solar diurnal change.”
http://www.tandfonline.com/doi/abs/10.3109/15368378.2013.809579