Near real-time high resolution and high precision ionosphere models are used for a large number of applications e.g. in navigation, positioning, telecommunications or astronautics. Today, these ionosphere models are mostly empirical, relying on extensively pure mathematical approaches. However, the complex phenomena within the ionosphere can only be understood and modeled when taking into account the physics behind the phenomena. In this project we present the basic structure of a model for the electron density of the ionosphere, which will be developed by a cooperation of DGFI, the Institute of Astronomical and Physical Geodesy (IAPG) of the Technical University Munich (TUM) and the German Aerospace Center (DLR), Neustrelitz.
The model will be based on series expansions in terms of physics-motivated mathematical functions such as the Chapman function. Introducing the Chapman function and a plasmasphere layer, altogether five parameters describe the vertical behavior of the electron density, namely the F2-layer maximum electron density (NmF2), the peak height (hmF2), the F2-scale height (HS) and the plasmasphere basic density (NP) and scale height (HP). The Figure below shows the vertical electron density profile with varying NmF2. In our approach, we decompose each of these parameters into an initial part, derived from given ionosphere and plasmasphere models, respectively, and an unknown correction term. The latter are modeled in series expansions in terms of tensor products of three one-dimensional B-spline functions depending on latitude, longitude and time. Thus, a combined physical-mathematical model is derived. All the unknowns of this model can be solved from space-geodetic observation techniques within an adjustment process and lead to the determination of a four-dimensional model of the electron density.
The main features of the project are (1) the consideration of physics-motivated modeling approaches, which are introduced in the multi-dimensional ionosphere model by means of appropriate mathematical base functions such as B-spline functions, (2) the estimation of the model parameters from the combination of various space-geodetic techniques, such as terrestrial and space-based GPS observations, altimetry and/or VLBI as well as (3) the transformation of the results into a multi-scale representation, which allows both an effective data compression necessary for handling the huge ionosphere data sets and near real-time applications as well as the identification of physical phenomena at different spatial and temporal scales. For testing the procedure, the model will be applied to an appropriate region in South America, which covers relevant ionospheric processes and phenomena such as the Equatorial Anomaly.