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Fig. 1.
Homogeneous atmospheric field at ground level Field strength ~ 150 V · m(-1) |
The origin of the atmospheric electric field is thunderstorms. At any given time about 2000 thunderstorms are active, creating a voltage difference of about 300.000 volt, between the lower part of the ionosphere and the ground.
The field will make airborne, charged particles move, the positive particles in the direction of the field, the negative in the opposite direction. The most important of the charged particles are the atmospheric ions (see for instance Niels Jonassen: IONS, Compliance Engineering, June/July 1999). The field-induced motion of the positive ions constitutes a current to ground with an average value of about 3 pA · m(-2) (3 · 10(-12) ampere per square meter). |
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Fig 2.
Inhomogeneous atmospheric field around mountain ridge or house roof. field strength ~ 1000 - 2000 V · m(-1) |
Fig 2.
Inhomogeneous atmospheric field around mountain ridge or house roof. field strength ~ 1000 - 2000 V · m-1 If now the surface considered is not horizontal the situation changes dramatically. In Fig. 2 is shown the field around a sharp structure, like a mountain ridge or maybe just a house roof. The field will no longer be homogeneous, but is said to be distorted, having values in the order of 1000-2000 V · m-1, i.e. about 10 times the values at a horizontal surface. Consequently the current to ground will be about 10 times as dense. |
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Fig. 3
Field between lightning rod and thundercloud Maximum field strength 3-4 MV · m(-1) |
A special case of a strongly distorted field is shown in Fig. 3.
We here have a house supplied with a (grounded) lightning rod. Above the house is a thundercloud with a negative base. We notice that the direction of the field lines is the opposite of that in fair-weather conditions, as shown in Figs. 1 and 2. The field strength has its highest value at the tip of the rod, and if the field strength here exceeds a critical value, the break-down field strength, of 3-4 MV? m(-1) (3-4 million volt per meter) an electric discharge takes place. The discharge may take the form of a silent corona discharge or it may start a violent and dramatic lightning discharge. The field strengths and currents will be much larger than with fair-weather conditions, but the point is, that in both cases a distortion of the electric field, caused by a sharp or pointed "electrode" will increase the current from the atmosphere to the electrode. |
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Fig, 4
Field around acupuncture needle |
And here we are finally approaching the topic of acupuncture.
In Fig. 4 is shown a finger with an acupuncture needle inserted. The finger and the rest of the body is assumed to be grounded and placed in a positive field, i.e. a field directed towards any grounded objects. In the absence of the needle the current to the finger, caused by the field will be distributed more or less evenly over the finger. |