  A high altitude nuclear electromagnetic pulse (EMP) with a peak field
intensity of 5 x 10^4 V/m carries momentum that results in a retarding force on
the average Compton electron (radiating coherently to produce the waveform)
with magnitude near that of the geomagnetic force responsible for the coherent
radiation. The retarding force results from a self field effect. The Compton
electron interaction with the self generated magnetic field due to the other
electrons accounts for the momentum density in the propagating wave;
interaction with the self generated electric field accounts for the energy flux
density in the propagating wave. Coherent addition of radiation is also
quantitatively modeled.
