High Altitude Bursts-Electromagnetic Pulse(EMP):
High altitude air bursts which are over 100,000 feet will cause very little ground damage or nuclear radiation. They are however, extremely effective in destroying radios, televisions, communications, telephones, internet...and other computerized equipment. Virtually any electronic device which relies on solid state construction or semiconductor rectifiers, including, but not limited to automobiles with electronic ignition, will very likely be destroyed by such an air burst. This is because the detonation creates an electromagnetic pulse (EMP) in the frequency range of micro waves and radio waves which induces electrical current to flow through conductors such as wires, cars, and pipes. The surge of electrical current thus created, though lasting only a few thousandths of a second, spike sufficiently high enough to "fry" the fragile circuitry components of such devices. This EMP electrical spike is so short in duration, and detonated so high that it does not effect individuals, in any other way. Unless, you just happened to be looking up in the sky, at that moment and saw a momentary "flash of light" you would have no idea that the "explosion" had occured. If you should see such a burst, never look directly at it because it can cause blindness, even from distances of up to 200 miles.
It has been estimated that electrical services and communications could be damaged or disrupted in an entire spectrum...or country by the High Altitude detonation of a single large nuclear weapon over the geographical center of the country. It is therefore likely that a "First Strike" against a specific country or region would probably begin with an unexpected "Surprise" high altitude detonation to create an EMP surge sufficiant to cripple communications, destroy All computer defense systems, and completely eliminate all radar tracking facilites. This would leave the entire Country, spectrum or region open to attack with no ability to defend itself...or shall we say...retaliate.
As an individual, should you ever experience a power failure, immediatly check your telephone, and battery powered radio. If they do not work try your car. If it does not work and other cars on the road have "Mysteriously" stopped...you will know that a high altitude nuclear device has been detonated and the resulting EMP has destroyed the communications system.
Low Altitude Bursts:
Low altitude bursts (2000-10,000 feet) are generally used to destroy "Soft" targets which are above ground. These type of bursts generally produce severe damage from heat, blast and initial radiation levels...but do not produce significant levels of radioactive fallout. Low altitude bursts are generally localized in their destructive ability...but they are totally destructive to that specific area. Their effects are as follows:
Blast:
The detonation of a nuclear weapon produces a powerful shockwave which travels at a high rate of speed in all directions from the "Blast Zone." This wave has two destructive components. The extremely rapid expansion that occurs in the blast causes compression of atmospheric air for many miles around and is called overpressure, measured in pounds per square inch (PSI). One PSI overpressure may be thought of as being one pound per square inch above normal atmospheric pressure for your area or altitude.
Overpressure exerts force on surfaces and will crush hollow objects such as cars and buildings. An overpressure of just 0.5 PSI, which can break windows and cause other damage in residential areas, could occur at a distance of twenty miles from a one megaton blast. An overpressure of 4.5 PSi is enough to flatten the average single family dwelling. This amount of pressure can occur at a distance of approxamately five miles from a one-megaton, or ten miles from a ten-megaton blast.
The second componant of a nuclear shock wave is called dynamic pressure and is characterized by a high wind which may reach speeds of one-hundred miles per hour at a distance of six miles from an air burst one-megaton blast, which is sufficient to knock over a person standing up.
After the shock wave passes the pressure falls until an underpressure, like a vacuum, develops and a reverse wind blows back toward the explosion. This reverse wind and vacuum, will also cause damage, but is not as severe nor as destructive as the initial shock wave.
Heat:
At the time of detonation the intense flash of rapidly expanding fireball, can start fires miles away. The extreme heat of the detonation will literally vaporize everything nearby.