Effects of Atmospheric Gravity Waves on the Propagation of VLF Signal

During typhoon activity, the atmospheric gravity waves (AGWs) will cause the Earth’s ionosphere to fluctuate, causing the equivalent reflection height of the ionosphere to change, resulting in an abnormal change in the phase of the VLF signal received by the receiving station. Therefore, This paper analyses the response of phase the VLF signal to atmospheric gravity waves, using the VLF monitoring system to study the VLF signal data received by the Xinxiang receiving station during typhoon “Dan” in October 1999, which was transmitted from the Novosibirsk launching station of the Russian Alpha navigation system. Then the effect of the atmospheric gravity wave on the VLF signal propagation is studied based on the waveguide mode theory. It is calculated that when the frequency of the VLF signal is 14.9 kHz on 9 October 1999, the phase change is 5.12 cec, and the phase change on 12 and 13 October is 4.36cec and 3.34 cec respectively. Space weather conditions, and solar flare data released by the GOES satellite were then analyzed and their effect on the phase of the VLF signal was excluded. The results show that the phase anomaly of the VLF signal is caused by the atmospheric gravity wave excited by the typhoon. Therefore, the effect of atmospheric gravity waves on VLF signal propagation studied in this paper could predict and correct the phase of VLF signals, ensure the accuracy of the VLF navigation system as GPS backup, and have great significance for improving the accuracy of VLF navigation and positioning.