Daytime and nighttime variations of VLF signal during quiet period

This paper presents variations of Very Low Frequency (VLF, 3-30KHz) during quiet days for the period of February, March and April 2010 that extracted from (UKM) Malaysia (2.55°N, 101.46°E) receiver station. The VLF amplitude data were observed from the nearest transmitter stations which are located at 3SB,China (39.26°N, 103.20°E), JJI, Japan (32.09°N, 130.83°E) and VTX, India (08.23°N, 77.45°E). The VLF wave propagate along the Earth-Ionosphere waveguide (EIWG) and recorded by the VLF observation system that established by Stanford Atmospheric Weather Electromagnetic System for Observation Modeling and Education (AWESOME). The analysis covered the VLF amplitude values during daytime and nighttime from three (3) transmitter stations. The results correspond well with the observed time frame, which is clarified ionization level of D-region place significant role of the VLF propagation. This finding is important in characterizing the variations of VLF wave with respect to electromagnetic propagation medium at D-region.