Geomagnetism and the paranormal
I know there have been studies showing apparent (though not highly significant) links between geomagnetic variation and the reports of paranormal phenomena, however I don't find them convincing. I suspect readers of such reports compare them with epidemiological studies used to pinpoint environmental causes of disease. However, there are major differences.
In an epidemiological study, diseases are diagnosed by professionals using fairly strict symptoms and confirmatory lab tests. The main causes of such diseases are often well-known. These can measured on site and then allowed for in the study so that other, novel, causes of disease can show up in the remaining data.
Compare this with the data used in studies of the distribution of paranormal reports. The quality of reports is highly variable. It ranges from full in-depth investigations by academics up to vague unchecked newspaper reports. Many of the people who investigate cases are not trained and some have distinct biasses towards belief or scepticism. It is highly likely that a significant proportion of the reports are either incorrect in detail or entirely spurious. In other cases, some otherwise good data may be rejected for spurious reasons.
Then there is the question of possible causes of reports. The fact is, we simply don't know many of these. There may be many as yet undiscovered causes which we obviously cannot eliminate. It is obviously not known how these unknown factors may affect each other. In addition, even known factors may not be measured or may be measured inaccurately during many investigations. For these reasons I think such surveys are premature and probably unhelpful.
With regard to geomagnetic variation, a single variable such as a planetary index is often used in a study to decide geomagnetic variability at any instant. However, these are overall average indicators (as the name implies) for the whole planet. The geomagnetic field shows regional variations as the effect of solar disturbances propagates along magnetic field lines in the magnetosphere. So, really, you need magnetic readings to be taken ON SITE where the paranormal report originated at the time it occured.
I am also sceptical about of any plausible mechanism for paranormal reports to be linked to geomagnetic activity. We are talking about a variation of up 0.5% (and usually VERY much less) in the overall geomagnetic field spread over a period of many hours! It is difficult to see how such a slight, slow variation could have any significant effect on people.