GROUND-BASED DIRECTION FINDING OF VLF RADIO WAVES BASED ON THE WAVE DISTRIBUTION FUNCTION: SOLUTION INDEPENDENT OF WAVE POLARISATIONS

摘要

We discuss a method for estimating wave distribution function (WDF) independently of wave polarisation, which is an important technique to discuss the propagation and generation mechanisms of VLF radio waves, including magnetospheric VLF waves, tweek atmospherics, waves from transmitter and so on. A new treatment to estimate WDF solution of VLF waves observed on the ground is discussed. This is very effective method to discuss the propagation and generation mechanisms of VLF radio waves, because it is possible to estimate the WDF, or wave energy distribution in wave number space. It is confirmed, by computer simulation, that this method is effective to discuss the propagation characteristics of VLF waves, and also it is found from analysis of VLF emissions that the ionospheric exit region moves very fast.