latitude and longitude, the peak and average power densities at the surface of the earth are ^230 watts/m^ and ^106 watts/m , respectively. There are several potential problems connected with beaming this much microwave energy to the earth from the SPS. Among these problems, briefly considered here, are the following: 1. Electrical breakdown in earth's atmosphere — no problem at any altitude. 2. Heating of earth's atmosphere — no problem at any altitude (other sources heat atmosphere more). 3. Disturbances of earth's ionosphere — no problem at any altitude (Luxembourg effect negligible here). 4. Interferences with RF communications — some problems with radio astronomy, tropospheric service, shipboard radar in vicinity of receiving station. 5. Biological hazards to men, animals — slight problem to wildlife in vicinity of receiving station. In the first case, electrical breakdown in earth's atmosphere, the following must be considered: • At frequency of 2.45 x 10$ Hz, an electron is accelerated in one direction for 2.05 x 10"10 sec. • At electric field of 294 v/m, electron acceleration is 5.2 x 10^3 m/sec^ • The maximum energy an electron can gain is 3.25 x 10"^ electron volt • This is too low to ionize anything by a factor of ^10^ • Therefore, no electrical breakdown will occur; effects on electrical discharges due to other causes (lightning, spark gaps, etc.) are negligible. The microwave energy transport will not cause electrical breakdown in the atmosphere, even at the Paschen minimum. An electron in the 2.45-GHz, 230-w/m2 field will gain only 3.25 x 10“4 ev during a half cycle (5.2 x 10-^3 m/sec^ for 2.05 to 10“^^ sec), which is approximately four orders of magnitude too low to ionize any atom or molecule. In the second case, heating of the earth's atmosphere, the following reasoning is used:
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