TY - JOUR AU - Tan, Le Minh PY - 2016/02/21 Y2 - 2024/03/28 TI - The responses of low-latitude D region ionosphere to solar flares during 2014 JF - Vietnam Journal of Earth Sciences JA - Vietnam J. Earth Sci. VL - 37 IS - 3 SE - Articles DO - 10.15625/0866-7187/37/3/7801 UR - https://vjs.ac.vn/index.php/jse/article/view/7801 SP - 275-283 AB - <table cellspacing="0" cellpadding="0" width="656"><tbody><tr><td align="left" valign="top"><p class="Abstract">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 (<em>h'</em>), and the electron density gradient (<em>b</em>). The results reveal that when the X-ray irradiance (<em>l</em> &lt; 1 nm) increases, the <em>b</em> increases from 0.31 to 0.53 km<sup>-1</sup>, while <em>h'</em> decreases from 72.8 to 60.9 km. The values of <em>h’</em> observed at low latitudes are higher, but the values of <em>b</em> 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.</p><div class="WordSection1"><p><strong>References</strong></p><p class="Tiliuthamkhonidung">Basak, T. &amp; Chakrabarti, S. 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