Understanding and modeling the solar wind: challenges, limitations and solutions towards better predictions

One of the biggest challenges in current space weather research is to predict the characteristics that the high speed solar wind streams will have when arriving at the Earth (or at other planets) based on properties of their source, the coronal holes observed at the Sun. The innovative simulation tool EUHFORIA (EUropean Heliospheric FORecasting Information Asset, Pomoell and Poedts, 2018) is a new heliospheric 3D MHD model that has been developed to simulate the solar wind and coronal mass ejections (CMEs). It presently models the arrival of high speed streams (HSS) at the Earth with different degrees of success, depending not only on the detailed characteristics of the HSS but also on the characteristics of the coronal holes located at the Sun. Therefore, it is of utmost importance to clarify the influence that the different coronal hole features will have on the modelled solar wind. For the purposes of the study, we will compare in situ solar wind data from the L1 point (and from other planets) with information from coronal holes, obtained using the CATCH software tool (a coronal hole analysis toolkit, provided by the University of Graz) and other relevant data obtained by spacecraft such as SDO, SOHO, PROBA-2, STEREO as well as from the upcoming missions Solar Orbiter, Parker Solar Probe and PROBA-3. Based on the results of this study, EUHFORIA will be modified to reflect the different types of the coronal holes and their effects on the fast solar wind. Furthermore, the HSS and the background solar wind influence the propagation of coronal mass ejections (CMEs). As CMEs are the major driver of space weather at the Earth, modelling of their evolution, propagation and impact is of fundamental importance in space weather science and operations. For this reason, the second part of the PhD project will be devoted to modelling of CMEs and their influence on the Earth, Venus and Mars. This part of the PhD project is complementary to currently running PhD projects at KU Leuven and Royal Observatory of Belgium. After the completed analysis of solar wind and solar CMEs, stellar CMEs in superflare stars are going to be simulated for the first time by using EUHFORIA, which constitutes the third part of the current PhD project. The modelling of stellar CMEs is of high importance and necessity in order to assess the possibility of surface, atmosphere-dependent habitability in Earth-like planets lying at the habitable zones of superflare mother stars. Overall, the ultimate goals of this project are to make EUHFORIA stand out among the current state-of-the-art MHD heliospheric models by improving its solar wind modelling, and to increase our understanding on the propagation of CMEs, including those from other stars. The scientific impact of this work deals with the correlation of coronal hole parameters with solar wind propagation, none of the current state-of-the-art MHD heliospheric models include this level of refinement. Moreover, the work will be extended to stellar CME simulations that will provide valid estimates for possible surface habitability of newly discovered planets in distant extrasolar planetary systems.