Condign volumes 1 to 3

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# UNCLASSIFIED

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## NON-IONISING EM EFFECTS ON HUMANS

## EM FIELD FROM A PLASMA

1. The EM field from a radiating plasma is assumed to be present in three forms:

- The Radiation field which diminishes with range at $ \frac{1}{R^{2}} $

- Induction components which diminish at $ \frac{1}{R^{2}} $

- A Quasi-Static field which reduces at $ \frac{1}{R^{3}} $

2. Near Fields The induction and quasi static fields are near field components, only of significance close to the source and thus of particular interest in the study of those UAPs which might be caused by plasmas or electrically charged bodies. Assuming that the dimension D (effective linear aperture) of the plasma is large compared with the wavelength $ (\lambda) $ , then the near field is taken to extend to a distance $ 2 \mathrm{D}^{2} / \lambda $ from the source. The Radiation Field (far-field) is not of interest in this study. In the normal case of an EM source (for example, antenna emission) the radiation field beyond the near field stabilises with spatially uniform distributions of the E and H field components, which are at right angles to each other and transverse to the direction of propagation, they are in phase and have a constant amplitude relationship.

3. UAP Near Fields Assuming that EM radiation may be present in at least some of the UAP sources (e.g. ball lightning, bead lightning, 'earth lights' and other charged airmasses, it is possible to calculate, as shown at Table F-2, some expected near-field distances.

4. For effects on humans calculations are made to determine power flux-density (watts/m $ ^{2} $ ). In the near field this value is determined from the vector product of the E and H fields, making calculation more complex than the familiar terms (S-PGi/4 $ \pi R^{2} $ ) used, for

example, for radar calculations. For the nearfield there is an arbitrary phase and amplitude relationship between E and H which must be taken into account for every point in the nearfield region if power flux-density values are required. To simplify calculations for the nearfield a plane-wave equivalent value is sometimes used. If the E field or H fields are known. power density is evaluated respectively from $ E^{2}/Z_{0} $ or $ H^{2}/Z_{0}. $ $ Z_{0} $ is the familiar characteristic wave impedance of free space 377 $ \Omega. $

5. It is not clear whether single, multiple or broad-band radiation frequencies are emitted from the airborne sources of interest (UAPs). Unfortunately there are no electric or magnetic field strength measurements taken. the majority of UAP events only being present for a few seconds.

6. Standard radiation hazard calculations assume that at MF/HF the frequencies are below whole human body resonance frequencies and direct hazard effects can be high. Most of the work concerning radiation levels concentrates on the specific absorption rates (SAR) in biological tissues (for thermal reasons). The maximum amount the body absorbs depends on the rate between body length and the free-space wavelength of 0.4. For the human body a significant absorption maximum therefore occurs at $ \sim 8 0 \mathrm{M H z} $ （ $ \lambda= $ 3.75m).varies with adults and children and is dependent on whether the subject is in contact with a conductive ground or in free space.

7. Variation with RF Below an RF of ~30kHz, thermal effects can be neglected in comparison to stimulation effects on nerve and tissue cells. In the RF range from ~100kHz to 1MHz the thermal and stimulation effects are of the same order. Figure F-1 shows the combined experimental results for RFs up to 100kHz. For the study of possible radiation