Ionospheric disturbances triggered by solar flare events during solar maximum — May 2013

A solar flare is a huge explosion in the sun's atmosphere. It produces a powerful burst of radiations which can severely affect the Earth's ionosphere and a wide range of radio communication services. One of the methods used to study the effect of solar flare is by continuously monitor and measure the Very Low Frequency (VLF 3-30 kHz) radio waves signal. Short term analyses of the data recorded by AWESOME receiver at Universiti Kebangsaan Malaysia, for the period of April to May, 2013 were presented. There were 5 solar flare events with classes greater than M1 (X-ray flux ≥ 1.0 × 10-5W/m2) recorded by GOES satellite which created 20 VLF perturbations during the observation period. Results indicated that the enhancement of X-ray radiation from the sun during the solar flare event was capable to generate VLF perturbations as high as 10 dB in amplitude and 85 degrees in phase signals. Three Transmitter Receiver Great Circle Paths (TRGCPs) propagating VLF signal over land and sea at frequencies 19.8, 22.2 and 21.4 kHz were analyzed simultaneously. The data from all TRGCPs confirmed the association between solar flare event and VLF ionospheric disturbances. The correlation coefficient between the solar flare X-ray flux intensity and the magnitude of the VLF perturbations for the studied flare event are presented.