Abstract
In this work, a solar illumination model of the Earth’s atmosphere is developed. The developed model allows us to determine with extreme accuracy how the atmospheric illumination varies during night hours on a global scale. This time-dependent variation in illumination causes a series of sudden changes in the entire Earth-atmosphere-ionosphere system of considerable interest for various research sectors and applications related to climate change, ionospheric disturbances, navigation and global positioning systems. The use of the proposed solar illumination model to calculate the time-dependent Solar Terminator Height (STH) at the global scale is also presented.Time-dependent STH impact on the measurements of ionospheric Total Electron Content (TEC) is, for the first time, investigated on the basis of 20 years long time series of GPS-based measurements collected at ground. The correlation analysis, performed in the post-sunset hours, allows new insights into the dependence of TEC–STH relation on the different periods (seasons) of observation and solar activity conditions.
Highlights
The dividing boundary between the day and night side of the Earth and its atmosphere is called Solar Terminator (ST)
Geomagnetic activity can significantly affect Total Electron Content (TEC) so that, in order to discriminate solar from other contributions, it is important to study those parts of the day when ionospheric layers are selectively illuminated by the Sun [32] (Figure 3)
Geomagnetic activity can Collection of TEC Data Samples significantly affect TEC so that, in order to discriminate solar from other contributions, it is important to study those parts of the day when ionospheric layers are selectively illuminated by the Sun [32] (Figure 3)
Summary
The dividing boundary between the day and night side of the Earth and its atmosphere is called Solar Terminator (ST). Solar illumination reaching the two sides of this region differently contributes to the energy balance at different heights in the atmosphere Such a differential, time-dependent, illumination generates sudden changes throughout the whole. A Solar Terminator Height (STH) model is proposed which provides, with unprecedented accuracy and at the global scale, the vertical variation of the ST as a function of time. In the post-sunset hours, the sudden variation in solar irradiation incident on the various ionospheric layers generates variation in total ionization Such a study can be useful in the elaboration of ionospheric TEC models as well as in those applications requiring predicting the behavior of TEC parameter in specific conditions. TEC models play in the study of the possible relations between ionospheric perturbations and seismic activity, theorized by several authors in recent years [19,20,21,22,23]
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