| MadSci Network: Physics |
In principle what you suggest is possible. An artificial arc was experimentally produced over 30m long. Since it was impractical to create high enough voltage or strong enough insulation to produce it directly, the arc was launched into the air by ionization, and steered by external electrodes, much as you suggest. In practice, the difficult part of taming the natural thunderbolt is you have little control or knowledge on the upper part of the circuit, the cloud. Large electrical charges are displaced through the earth mirroring the charges above, until the thunderbolt discharges them. At the ground, you can control thunderbolts more easily by simply controlling the height of the grounded objects. This is the "lightning- rod" developed by Dr Benjamin Franklin. It naturally takes advantage of the factor "inversely with the square of the distance", by increasing the height of the rod we reduce the distance to the cloud and increase the attraction. The field gradient is how steeply the voltage changes. At low gradients we can apply electrical charges to change the shape and gradient of the field near the rod. However, the natural voltage will reach many thousands of volts per cm before a thunderbolt strikes, so at a distance away from the rod any artificial voltage that we could achieve has very small effect on the total field. If we could watch lightning form in slow motion, we would normally see a dim "stepped leader" about 1m diameter descending in steps of about 50m, with a short pause between each step. This establishes a channel that would be followed by several "return strokes" that follow the channel upward, delivering the electrical energy that produces the bright flashes we see. To control the path of the return stroke, one must control the evolution of the stepped leader. NASA Primer on Lightning: My web page has some electrical data on lightning The "Earth Circuit" has a voltage of 500,000 volts + upwards, at a height of about 80 km all over the earth. The total capacitance is about 0.25 Farads with a leakage resistance of 200 ohms, and leakage current of 2500 amperes, that would deplete the charge in less than one minute. The combined atmospheric electrical activity over the earth constantly replaces this charge, delivering about 1250 megawatts of power. The entire "Earth Circuit" is equal to almost 2% of the electrical power needs of India. Best Regards, Altair www.altair.org
Try the links in the MadSci Library for more information on Physics.