The Safety of ELF Fields Generated in the Ionosphere

The process of generating ELF within the ionosphere is very inefficient (the conversion efficiency is about $10-8$). As a result, the level of ELF signal reaching the ground is extraordinarily small. Measurements of the ELF signal strength produced in the ionosphere by the HIPAS facility during a recent test, for example, showed field strengths on the order of 5 pT or 0.00005 milligauss (mg)[1]. This field strength is too weak to be detected with any commercially available instrument and is only useful for low data rate communications or for geophysical sensing applications where specialized correlating receivers can be employed.

The subject of ELF safety has received significant attention in the US and around the world, primarily because of concerns over the fields produced by High Voltage power lines, but also because of concerns over such common ELF sources as household appliances and video display terminals (VDTs). Concise summaries of some of these studies and additional information on radio frequency radiation (RFR) can be found at EMF Link operated by The EMF Clearinghouse.

Here are some comparisons between the signal levels that could be produced by ionospheric heating and some more common, day-to-day activities:

• A draft report prepared for the Environmental Protection Agency (EPA) recommends an ELF exposure limit of 2 mG for new day care centers, schools and playgrounds. The EPA which funded this study, called it "the most comprehensive study ever on the health effects of low frequency EMFs." [2]. ELF fields that can be produced by HAARP are 400,000 times weaker than this "safe" level."
• According to Consumer Reports [3], "US homes typically have a "background" field level ranging from 0.1 to 2 milligauss (mG), the standard unit of measurement for magnetic fields. Epidemiologic research on exposure to EMFs, then, has focused on fields measuring above 2 or 3 mG." Background fields in a typical household are 400,000 times stronger than the strongest ELF field ever produced by ionospheric heating.
• The ELF field strength level at arm's length distance from a computer video display terminal (VDT) is typically 2 mG. Consumer Reports suggests that users "... practice "prudent avoidance" by sitting at this distance." [3] This is a field strength 400,000 times stronger than the ELF field produced by ionospheric heating.
• Concern over ELF fields has even extended to the field produced by stereo headphones. According to a recent study [4], the field produced at the outer layer of the brain by typical headphones was measured to be 0.15 - 0.75 mG. The study points out that these levels of field are about half the level at which some researchers have reported biological effects in animals. This still represents a field strength approximately 100,000 times stronger than the ELF field that could be produced by HAARP.
• Even if all appliances and all electric utilities were turned off, the ELF field that could be produced by ionospheric heating would be less than the naturally occurring background noise field caused by worldwide thunderstorm activity.
• Time varying magnetic fields can be produced simply by moving through the earth's constant, static natural field. For example, magnetic field strengths that are produced by running, driving a car, or even sitting still and nodding your head rapidly are greater than the background ELF fields commonly found in homes [5]. Fields that could be produced by HAARP are, in turn 400,000 times weaker than this.

We have provided a stereogram to illustrate the point that ionospheric ELF fields are so weak that to detect them requires special processing methods. When you look at this stereographic image, you will see a great deal of "noise," in a direct analogy to the problem faced by ELF receivers which must be sophisticated enough to pick out a very weak signal in the presence of naturally occuring background noise or static. There is a message buried in this noise along with a picture that is even more difficult to see. The message is readable but only by using the special processing power provided by two eyes. You need to sit about an arm's length from the monitor to view this message (for safety reasons too!). Thanks to Tony Frazier-Smith of Stanford University for creating this image

References

[1] McCarrick, M. J., et al, "Excitation of ELF waves in the Schumann resonance range 
    by modulated HF heating of the polar Electrojet," Radio Science, Vol 25, Nr 6, 
    pp 1291-1298, Nov - Dec 1990.
    
[2] New Scientist, October 7,1995, p. 4

[3] Consumer Reports, May 1994.

[4] Baumann, S and Alagarsamy, S., Meeting abstract from Bioelectromagnetics Society, 
    12th Annual Meeting, 10-14 June, 1990.

[5] Bennett, William R. Jr., Health and Low Frequency Electromagnetic Fields, 
    Edwards Brothers, Inc: Ann Arbor, MI 1994. p. 95.

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