Quote:
Originally Posted by J_Player
Hi Rudy,
You are correct. An instrument which stimulates the target area will necessarily work diffrently than a passive instrument which measures only natural state signals. As an example, a conventional metal detector measures signals that don't exist naturally in any measureable amound from the buried metal. A passive detector in the case of buried metal is looking for a much smaller signal which is more likely to be buried in noise, and more difficult to find. This means you would need to make an exhaustive search to find the most likely kind of signal that will be strong enough to measure.
The most likely candidate for a passive signal seems to be the atmospheric air charge. Everything else is tiny in comparison. As far as a large electric field gradient, this is the standard gradient in the air, driven by solar wind at the ionosphere. It varies from day to night, and from season to season, and even has local variations. But it usually falls in the range of 100-200 volts per meter altitude in the vicinity of the earth surface. See here for my previous discussion of this: http://www.geotech1.com/forums/showt...688#post126688
The current leaking into the air is typically around 11.76 nA leaking from any 1 sq meter of earth surface on average. Of course we can't measure this current with any normal kind of milliammeter, but we can expect it will change to maybe double if the conductivity of the ground is caused to change to double the amount in found neighboring areas. The theory is that chemical reactions of corroding buried metals will change the conductivity of the ground to become higher than ground with no chemical activity involving metal corrosion. When this happens, we could expect the 100 v/meter gradient to be reduced in this local area of higher ground conductivity and higher current leaking into the air. This reduced voltage gradient should be easier to measure because it is in a range where we have instruments that can measure it.
The only problem I have with this theory is I haven't seen any field data to support it. It would be interesting to see some actual tests that show the field gradient over uniform ground that has places where a conductivity/resistivity anomaly is created in the soil. In a test condition, the conductive soil area can be made by simply pouring water into a small hole and giving it time to absorb into the soil. Or maybe by driving a long metal rod into the ground to conduct to the lower layers, then pouring a bucket of water on the top surface.
I am suspecting that if a zahori is very sensitive to electric field variations it will detect this variation in gradient. Of course, the same variation in gradient could be caused by a damp spot in the soil where an animal recently visited. This could result in finding a questionable treasure. 
Best wishes,
J_P |
Hmm, interesting. I would surmise that during normal weather (not a thunder storm), the source resistance for this 200V/m electric field must be very high since the air molecules are mostly not ionized and the air therefore acts as a dielectric medium.
The presence of the human hunter must then have a significant effect on the electric field in his immediate surrounding, given his relatively low resistance, specially on a hot humid day. One can model the human resistance roughly as an outer resistance and an internal body resistance, where the skin resistance is of the order of 2,000Ω or less if sweaty, and the internal body resistance on the order of 500Ω. The resistance to ground (forgetting shoes for the moment) is then:
Rbody = Rskin(in) + Rinternal + Rskin(out)
Since we get from the external skin to the lower resistance internal organs and back to the external skin.
So Rbody ~4.5 KΩ maybe less if sweaty.
Assuming a 2 meter height for the human, We would effectively have 400 V from head to feet and Ohm's law would say that we'd have almost 90 mA of current flowing through us, a lethal amount.
Of course, we won't die because the source impedance behind that electric field is so high that it can't provide that kind of current. But, wouldn't our mere presence be sufficient to collapse that electric field in our vicinity?