SOME ASPECTS OF THE LWPC MODEL USAGE IN GEOPHYSICS PROBLEMS

Abstract

The LWPC radio-physical model is intended for calculating the propagation of VLF-LF radio waves in the earth-ionosphere waveguide channel. It is an open-access program. Thus, many ionosphere and atmosphere geophysics researchers use the program as a tool for verifying the models by comparing theoretical results with the radio-field measurements. However, it is necessary to know what accuracy LWPC provides and what the influence of various model parameters is in order to obtain correct conclusions. This information is not available in the program user’s guide, so this work makes an attempt to compensate for this shortcoming. Analysis of considered variants allowed us to draw the following conclusions. The accuracy of the model is ~0.1–0.5 dB for amplitude and 1° – 5° for phase and depends on the path (coordinates of the transmitter and receiver and frequency). The program reaches this accuracy when specifying the ionosphere with a step of 100–150 km along the path. Replacing the built-in models of the ground conductivity and the Earth’s magnetic field by actual versions does not have a significant impact on the calculation results. The fundamental difference was obtained by replacing the collision frequencies, which are based on the standard exponential altitude dependence, with values calculated according to the distribution of neutral medium parameters. In this case, the difference in amplitudes reaches several decibels, and phases – several tens of degrees.