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Abstract

There are growing concerns about the effect of solar flares and Coronal Mass ejections on the ionosphere, due to possible deterioration or damage to our communication and navigation systems. An explosion on the Sun's surface that starts near a sunspot group in the photosphere or solar chromosphere releases a lot of electromagnetic energy. This kind of space weather event releases energy in the form of radiation in the entire electromagnetic spectrum. However, the UV, EUV, and X-ray radiation burst penetrates deeper into the Earth's atmosphere and will be absorbed in the D, E, and F regions. On July 3, 2021, and October 28, 2021, there were solar flares classified as X1.59 and X1.0, respectively. The first one (X1.59) took place between 14:18 UT-14:34 UT and the second one took place between 15:17-15:48 UT. These two solar flares are used to investigate the spatial-temporal electrodynamics of the ionosphere using observations from GPS-TEC. During both events, the South American, African, and European sectors were sunlight and exposed to solar radiation. Therefore, using VTEC and the parameters ROT and ROTI to investigate the ionospheric spatial-time dynamic and EIA response due to the solar-flare disturbances. It is noted that it is difficult to see any significant spatial-temporal ionospheric change when the VTEC is used. During the solar flare, ionospheric disturbances can be detected using the parameters ROTI and ROT. In conclusion, we are demonstrating that ROT and ROTI are the most appropriate parameters for studying rapid and small VTEC changes.