High-altitude nuclear explosion  From Wikipedia, the free
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altitude nuclear explosion) Jump to: navigation, search How the
peak EMP on the ground varies with the weapon yield and burst
altitude. Note that the yield here is the prompt gamma ray
output measured in kilotons. This varies from 0.1-0.5% of the
total weapon yield, depending on weapon design. The 1.4 Mt total
yield 1962 Starfish test had an output of 0.1%, hence 1.4 kt of
prompt gamma rays. (The blue 'pre-ionisation' curve applies
where gamma and x-rays from the weapon's primary stage ionise
the atmosphere, making it electrically conductive before the
main pulse from the thermonuclear stage. The pre-ionisation can
literally short out part of the final EMP.)  High-altitude
nuclear explosions (HANE) have historically been nuclear
explosions which take place above altitudes of 30 km, still
inside the Earth's atmosphere. Such explosions have been tests
of nuclear weapons, used to determine the