# A High Latitude Model for the E Layer Dominated Ionosphere
## 1 Introduction
They investigated the variations of these parameters as a function of season, solar activity, geomagnetic activity, interplanetary magnetic field, convection electric field and solar wind energy using COSMIC IRO data covering the period from 2006 to 2018. The authors found clear dependencies between the selected geophysical quantities and the considered ELDI parameters. In addition to the variation in the occurrence rate of ELDI events with maxima in winter and at low solar activity, the authors also observed an increase in their number, as well as a shift in their distribution toward the equator for rising solar wind parameters and related geomagnetic activity indices. While previous studies on the ELDI have dealt explicitly with its observations, the primary objective of the present work is to develop an empirical model describing main features of ELDI events. In this context, we use a modeling approach similar to other ionospheric parameter models previously developed at the German Aerospace Center (DLR) in Neustrelitz. Space-based single frequency navigation systems require a correction for the signal delay caused by the ionosphere, which depends on the total electron content (TEC) along the ray path. For predicting the vertical TEC, [PERSON] et al. [19] developedthe global Neustrelitz TEC Model (NTCM) based on TEC data generated by the Center for Orbit Determination in Europe at the Astronomical Institute of the University of Bern. Since the F2 layer exhibits the highest ionization of all the ionospheric layers, it has the largest influence on trans-ionospheric radio wave propagation. Considering this, [PERSON] and [PERSON] [20] developed the Neustrelitz Peak Density Model (NPDM) for describing the peak ionization \(NmrF2\) of the F2 layer. The model is based on a large dataset of vertical sounding data from ionosonde stations and radio occultation observations from the CHAMP, GRACE and COSMIC missions. By using the same datasets, [PERSON] and [PERSON] [21] also developed the Neustrelitz Peak Height Model (NPHM) for describing the peak ionization height \(hmF2\) of the F2 layer. Each of the aforementioned models follows a nonlinear multiplicative approach and is implemented by a parametric function. These functions consist of several nonlinear terms, which are linked to each other in a multiplicative manner and depend on one model driver each. Overall, this leads to relatively compact models for the key observables with a small number of coefficients (up to 13 in the case of the aforementioned models). The proposed Neustrelitz ELDI Event Model (NEEM) is composed of four submodels, whose respective model observables describe one aspect of the ELDI each. In this context, the submodel NEEM-P specifies the ELDI occurrence probability (%\(ELDI\)). While this observable indicates a change in the E layer's propagation characteristics, the associated E layer observables indicate how these characteristics change in the case of an ELDI event occurring. In this regard, we represent the observables peak ionization (\(NmE\)), peak height (\(hmE\)) and vertical profile width (\(wvE\)) by the submodels NEEM-N, NEEM-H and NEEM-W, respectively. Based on our previous studies, we select the geomagnetic latitude, local time, day of year, solar activity and the solar wind related convection electric field as user friendly and viable model drivers. Even though we give initial physical explanations for the dependencies found between the model observables and the model drivers, the focus of the present paper is mainly on the modeling of these dependencies. In this work, we use vertical electron density profiles derived from IRO observations onboard the COSMIC satellites. Since the satellites have an orbital inclination of 72\({}^{\circ}\), these observations cover a large area of the Earth's surface, including the auroral zones. Our database consists of approximately 2.3 million profiles covering a period of more than one solar cycle from April 2006 to December 2018.