The responses of low-latitude D region ionosphere to solar flares during 2014
93 solar flare events were recorded by using the Very Low Frequency (VLF) wave, 19.8 kHz from North West Cape (NWC), Australia to Tay Nguyen University (12.65°N, 108.02°E), Vietnam during 2014 to study the responses of the low-latitude D region ionosphere to solar flares. The observed VLF amplitude and phase perturbations are used as the input parameters for the simulated LWPC (Long-Wavelength Propagation Capability) program, using Wait’s model of lower ionosphere, to estimate the Wait’s parameters, the reference height (h'), and the electron density gradient (b). The results reveal that when the X-ray irradiance (l < 1 nm) increases, the b increases from 0.31 to 0.53 km-1, while h' decreases from 72.8 to 60.9 km. The values of h’ observed at low latitudes are higher, but the values of b are lower than those observed at middle latitudes during perturbed conditions. The representation of the electron density changes with altitude and time supports to deeply understand the behavior of the D-region ionosphere during solar flares.
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