NoiseProp: A Dynamic 60 kHz to 30 MHz Atmospheric Radio Noise Model

摘要

This report describes a broadband (60 kHz to 30 MHz) electromagnetic backgroundnoise model (NoiseProp). The model is conceptually similar to the PSR longwave noise model LNP, released in 1991. Global distributions of lightning activity divided into seasonal and diurnal maps are used to determine a set of elemental noise transmitters. The power radiated by each transmitter is proportional to the lightning flash rate at that location and to an empirically determined energy spectrum (which varies roughly as f to the minus second power 2). The radiated power is then propagated by a variety of propagation algorithms (LF, MF, HF) to the receiver. The overall noise power at the receiver is taken to be an incoherent sum of power propagated from each significant noise transmitter. The report additionally describes methods developed which will certain up-to-date and forecasted weather data to be converted to lightning activity (flash rate) maps. In this way, the NoiseProp model can be made to predict atmospheric noise dynamically rather than simply long term median values. A Windows-95 based graphical user interface for the NoiseProp has been developed and is described in the Appendix.