Abstract
This paper presents a new empirical model for predicting the daily mean ionospheric Total Electron Content (TEC) at a given latitude from only one solar index as input. For the development of the model we take advantage of the availability of 15 years of global GNSS-based TEC information and solar indices (Sunspot Number, F10.7 and derived F10.7P) including the 23rd solar cycle. Among all the tests, our preferred ionospheric climatological model to predict daily mean TEC presents yearly median differences with observed values of 1.4 ± 0.9 TECu (11.5 ± 2.9% for the relative differences) with no significant degradation during the different phases of the solar cycle. To realize this empirical model we used a least-square adjustment with (1) a combination of linear, annual and semi-annual terms between the TEC and F10.7P; (2) a discretization with respect to the phases of the solar cycle. The main differences between the modelled and the observed TEC occur during identified geomagnetic storms: the maximum differences (−3.2 ± 1.5 TECu) and relative differences (−19.6 ± 15.0%) occur one day after the storm onset. The typical time to retrieve the pre-storm conditions is 3–4 days after the onset. These results show a global picture of the effect of extreme Space Weather events on the Earth’s upper atmosphere.
Highlights
An increasing demand on a better modelling and understanding of the behaviour of the ionosphere-plasmasphere system is required by the scientific community which uses electromagnetic wave signals passing through this system
We developed a new empirical model to predict the climatological behaviour of the ionosphere at a global scale (S80°–N80°)
Our model allows the estimation of the daily mean Total Electron Content (TEC) at a given latitude from only the F10.7P parameter as input
Summary
An increasing demand on a better modelling and understanding of the behaviour of the ionosphere-plasmasphere system is required by the scientific community which uses electromagnetic wave signals passing through this system. One of the future challenges of the Space Weather community is to predict the Earth’s ionospheric-plasmaspheric TEC in response to variations of the solar activity and geomagnetic storm events. Many studies and models concerning the ionospheric state during quiet and geomagnetic storm periods were based on long-term ionosonde data (e.g., Rishbeth 1998; Tsagouri et al 2000) for different latitudes and solar activity levels. 1) during the entire 23rd solar cycle in order (1) to develop an empirical ionospheric climatological model to predict the mean daily TEC at a given latitude taking only one solar index as input and (2) to analyse the variation of the TEC during identified geomagnetic storm events. The minimum GDMTEC is 5.4 TECu and occurs during minimal solar activity in 1996 while a maximum of 54.2 TECu is observed during maximal activity in 2001
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