The effect of neutral mass density data assimilation on the quality of thermosphere-ionosphere state estimation

Abstract

Physics based models play an important role in the analysis of the complex coupling processes between the ionosphere and the thermosphere and predicting the processes happening in the upper atmosphere. The Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model and the Thermosphere Ionosphere Electrodynamics General Circulation model (TIE-GCM) are two state-of-the-art numerical models commonly used for that purpose. However, the quality of the results of the physics-based models depends on the accuracy in the estimation of the external forcing of the system and the accuracy of the initial state of the thermosphere-ionosphere system. In order to investigate to what extent the assimilation of in-situ neutral mass density helps to improve the estimation of the state of the thermosphere-ionosphere (TI) system, we will assimilate accelerometer-derived neutral mass density from CHAMP and compare the model results with GRACE data to evaluate the improvement in the thermosphere. In the same way, we will analyze the differences with Total Electron Content (TEC) measurements from the International GNSS Service (IGS) to assess the changes in the ionosphere due to neutral mass density assimilation. Therefore, the method will allow us not only to quantify the improvement in the estimation of the TI system, but to expand our understanding of the coupling mechanisms between the thermosphere and the ionosphere. Since this analysis might depend on model capabilities and implementation of data assimilation schemes, we approach this task with two different models and data assimilation schemes. A Thermosphere-Ionosphere Data Assimilation (TIDA) scheme has been implemented to the CTIPe model and the Data Assimilation Research Testbed (DART) has been coupled to TIE-GCM model. By this means, differences in model capabilities can also be indicated.