An Empirical Model of Ionospheric Total Electron Content Based on Tide-Like Signature Modeling

Accurate modeling of the total electron content (TEC) benefits scientific research and practical application. In this study, the global ionospheric maps from the Center for Orbit Determination of Europe (CODE) covering the years 2000-2021 are utilized to develop an empirical model of TEC by superposing the tide-like components in the ionosphere. The tide-like components, including the migrating and non-migrating ones, are first derived from the daily CODE TEC data. Then, the sine and cosine components of a tide-like signature are separately decomposed into the basic modes as a function of the modified inclination latitude with the principle component analysis, and the temporal evolution is regressed to the solar radiation dependence and interannual variation. As such, the climatological behavior of tidal amplitudes and phases could be well parameterized, and the developed model is capable of reproducing the global TEC patterns. The modeled TEC agrees well with the CODE input data with zero systematic error and a low root mean square error of 3.849 TECu, demonstrating a good model performance. This developed model, associated with the parametric tide-like signatures, could serve as a background for future investigations of the ionospheric responses to the forcing from below or above. The diurnal variabilities in the ionosphere could be expressed as a superposition of the tide-like components. The evolution characters are distinguished between these tide-like components, because their driven sources are different, including the diurnal photo-ionization by the solar radiation, the tidal forcing from below, and the nonlinear interactions inside. Previous works are generally concentrated on the variations in the amplitudes of the tide-like signatures, especially on their responses to the space weather events, while the attention to the phases' changing is limited. In this work, the solar radiation dependences and the interannual variations of the sine and cosine components of each tide-like signature are parameterized separately, so that the climatological behaviors of the amplitudes and phases can be reproduced simultaneously. Based on this approach, the global TEC patterns and the tide-like signatures could be consequently reconstructed, which provides a parametric background of the ionosphere for practical application and scientific research. An empirical model of total electron content is developed based on the superposition of the tide-like componentsThe seasonal and interannual behaviors in the amplitudes and phases of tide-like signatures in the ionosphere are reproducedThe developed empirical model has a good performance in reconstructing the variabilities in the global ionosphere