Lightning Mapping Array Source Powers

There are several Lightning Mapping Array's (LMA's) in operation around the country, that can locate VHF sources from lightning in 3-D and time. Another component that is also recorded is the received power at each station, and has not been fully utilized. The past calculations done by New Mexico Tech assumed an isotropic source and took a median value of the recorded source powers, not accounting for the antenna pattern or the ground interference. The NMT LMA uses a one half wavelength dipole antenna, and the height of the antennas above ground is known. For VHF the ground is neither a dielectric nor a conductor, but a complex combination with reflections that can be solved for numerically. The derived solution for the antenna pattern as a function of elevation angle is in good agreement with the empirical results. Once the antenna pattern is accounted for, it is possible to look at individual sources and see if they are indeed isotropic. It has been proposed that certain discharges, sferic Narrow Bi-polar Events (NBEs), which are often associated with high power VHF sources, have relativistic beaming effects. Another possible use of the powers is to look at the overall lightning and look for patterns in the storm data. During STEPS 2000 there were three power related results. First, as the source power increased so did the source altitude, possibly due to convection strength of the storms. Second was that the high power VHF events and associated NBEs, were predominately outside the core of the storm, with respect to both reflectivity and density of low power sources. The maximum source power in a storm increased with the storm size, either due to a more intense storm, or just a probability distribution effect due to a 1/P relation.