The effect of variability of ground conductivity on the calculation of atmospheric noise using thunderstorm-based models


  • Jerry A. Ferguson


Radio emissions from lightning discharges in thunderstorms are the primary source of atmospheric radio noise at very low and low frequencies (10–60 kHz). Attenuation of the lightning-induced signal between a source in a thunderstorm and a receiver occurs mainly by absorption in the ionosphere and in poorly conducting ground. The attenuation in poorly conducting ground depends primarily on the conductivity so uncertainty in this conductivity contributes directly to uncertainty in calculating the level of atmospheric noise. A thunderstorm-based computer model of atmospheric noise is used to evaluate the effect of this uncertainty in ground conductivity on calculation of atmospheric noise. It is found that this model produces only small variations in the level of atmospheric noise when the conductivity of the ground is varied. This result occurs because it employs large numbers of sources which tend to mask variations in the signal level on paths which cross low-conductivity ground.