No. 46: Jul-Aug 1986
"Several researchers have reported that poltergeist episodes frequently began on the day (± 1 day) of a sudden and intense increase in global geomagnetic activity. To test this visual observation, a near-complete account of these episodes for which the inception dates were recorded and verified was examined. Statistical samples clearly indicated that global geomagnetic activity (aa index) on the day or day after the onset of these episodes was significantly higher than the geomagnetic activity on the days before or afterwards. The same temporal pattern was noted for historical cases and for those that have occurred more recently. The pattern was similar for episodes that occurred in North America and Europe. The results were statistically significant and suggest that these unusual episodes may be some form of natural phenomena that are associated with geophysical factors."
(Gearhart, Livingston, and Persinger, M.A.; "Geophysical Variables and Behavior: XXXIII. Onsets of Historical and Contemporary Poltergeist Episodes Occurred with Sudden Increases in Geomagnetic Activity," Perceptual and Motor Skills, 62:463, 1986.)
Comment. To put this interesting item in perspective, one must realize that few established scientists recognize the reality of poltergeists.