Electromagnetic Pulse in Wide-Angle Gamma Shadows

Abstract

Unavoidable masses external to the warhead, associated with collateral EMP scenarios of current interest, produce a gamma shadow which changes the EMP seen in the shadowed region compared to that in the absence of a shadow. Calculations with the author’s three-dimensional MACSYNC code for a ground observer under the burst show shadowed field rise times ranging from many tens to hundreds of microseconds, durations approaching a millisecond, and magnitudes similar to those of the unshadowed field, depending on gamma shadow angle. These fields are likely to be smaller for larger observer ground ranges because the source region will shift to higher altitudes with associated higher conductivity that will attenuate the field.