Ground level signal strength of electromagnetic waves generated by pulsed electron beams in space

A theoretical study has been made of the signal strengths at ground level of waves generated by pulsed electron beams in space. Such beams might be generated by pulsed electron guns aboard either a satellite or a rocket. The radiated energy is first calculated by an improved version of a theory based on coherent spontaneous emission. This theory evaluates the electric and magnetic field strengths and power fluxes in the far field by applying asymptotic expansion techniques. With this information at hand, the power flowing out within a cone whose apex is located at the gun position is calculated. Finally, the intersection of the rays in this cone with the Earth's surface is determined by using Snell's law considerations. Ground signal levels are calculated for typical ionospheric conditions as a function of pulsing frequency for fixed beam voltage and for voltage adjusted for resonance between the waves and the particles. For short beams, the ground level signal strengths are relatively insensitive to the wave particle resonance condition, but for longer beams the associated peaking of the signal level begins to be observed. Finally, these results are compared against ambient noise levels to determine under which circumstances these ground signals can be detected.