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Other Nuclear Weapon Effects

     The large quantities of ionizing radiation produced by a
     high-altitude, high-yield nuclear detonation can severely change
     the environment of the upper atmosphere, producing heavily ionized
     regions which can disrupt electromagnetic waves passing through
     those zones. These disturbed regions can easily be the size of
     North America and can persist for tens of hours. The trapping
     mechanism for these high-energy electrons may be similar to that
     which produces the Van Allen radiation belts.

     The actual degree of communications interruption is dependent upon
     the scenario and includes weapon yield and HOB, time of day, cloud
     cover, latitude and longitude of the burst, the specific
     communications path, and the time after the detonation. Other
     systems which may be affected by nuclear weapons effects on
     electromagnetic wave propagation include sensors in the IR,
     visible, and UV regions, and laser communications which may be
     affected by the background IR. A very hot (but transparent) region
     of the atmosphere can act as a lens to refract a laser
     communications beam off of its intended receiver.

     Radar beams are both attenuated and refracted when passing through
     a nuclear fireball at altitudes below 25 km. At these altitudes
     the mean free path is small, and it is reasonable to speak of the
     fireball as being in local thermal equilibrium. Under these
     circumstances it is difficult to track incoming reentry vehicles
     (RV). Optical systems will suffer increased noise levels both
     because of ionized regions and from blackbody radiation from the
     fireball, and long-wave infrared (LWIR) systems may be unable to
     see through the fireball to an RV in the distance and may not be
     able to see an RV nearer to the sensor than the fireball because
     of the background.

     No high-altitude nuclear tests have been carried out by the United
     States since the ratification of the 1963 Limited Test Ban Treaty
     (LTBT). Apparently, few IR data were obtained from the CHECKMATE,
     KINGFISH, ORANGE, and STARFISH high-altitude tests, so the visual
     information from those tests has been extrapolated to the IR
     regime. The main sources of high-altitude IR which would produce
     clutter include plasma emission, molecular and atomic emission
     from excited states, and emission from uranium oxide. All of these
     are functions of electron density.

     At frequencies above about 300 MHz (UHF, SHF, and EHF), signals
     may be disrupted by scintillation, primarily characterized by
     intermittent fading and multipath transmission. These effects may
     persist for long periods and can degrade and distort a signal
     almost beyond recognition (for example, the plasma clouds are
     dispersive so that the speed of all frequencies of electromagnetic
     radiation are not equal in the cloud). Temporal and frequency
     coherence can both be destroyed.

     The vast majority of information relating to the propagation of
     electromagnetic radiation in a nuclear environment is pure
     science, primarily ionospheric and auroral physics including such
     phenomena as whistlers between northern and southern hemisphere
     locations. It requires no protection, but information on the
     mitigation of the effects may be classified because of
     considerations applicable to specific systems.

     All five of the declared nuclear weapon states, the United States,
     Russia, the UK, France, and China may have some capability to
     determine the effects of nuclear environments on electromagnetic
     signal propagation. All have access to and/or have contributed to
     the unclassified literature on RF propagation through structured
     media. The United States and the UK have provided models for
     calculating line-of-sight communications effects; the status of
     similar models in the other three nations is unknown.

Sources and Methods

   * Adapted from - Nuclear Weapons Technology Militarily Critical
     Technologies List (MCTL) Part II: Weapons of Mass Destruction
     Technologies

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Updated Wednesday, October 21, 1998 4:35:26 PM