The role played by coronal holes in solar wind forecasting

The space between the planets in our solar system is not empty but is filled with smaller pieces of the Sun itself. The discovery that the outermost part of the Sun`s atmosphere, the solar corona, expands much further into interplanetary space in form of the so-called solar wind is a milestone in the history of modern astronomy. The solar wind is an ever-changing stream of charged particles carrying the solar magnetic field away from the Sun enveloping our planet Earth. Earth`s magnetic field is frequently disturbed by the interaction with solar wind flows and fields causing geomagnetic storm activity. Severe geomagnetic storms are a challenge for the infrastructure of our modern society relying on spaceborne technology. This emphasises that accurate forecasts of background solar wind streams are of great importance in successful space weather awareness. Here we will use observational data from recent spacecraft missions to detect the source regions of fast solar wind flows, so-called coronal holes and link their physical properties to the solar wind flow in the near- Earth environment. We will systematically study the results on the basis of newly proposed solar wind model approaches and compare their performance to existing state-of-the-art models. From the here proposed research we expect new insight into the physical properties of coronal holes and valuable information on their role played in solar wind forecasting. This research project will be carried out by Martin A. Reiss at NASA Goddard Space Flight Center, and at the Space Research Institute of the Austrian Academy of Sciences.

Solar storms are not only responsible for impressive auroras, but can also significantly affect our power grids and disrupt modern satellite technology. Moreover, solar storms pose a risk to manned space missions. The more our modern society depends on space technologies, the more crucial it is to develop an understanding of the evolving ambient solar wind and associated dynamics called space weather. The ambient solar wind is a continuous stream of charged particles evolving through our solar system, starting from the Sun and interacting with Earth's magnetic field. The interaction of the solar wind with the Earth's magnetic field continually leads to enhanced geomagnetic activity, which can disrupt technologies in space as well as on Earth. This Erwin-Schrödinger fellowship aimed at deepening our understanding of the origins of the solar wind and its evolution in the vast reaches of our solar system. Based on magnetic field measurements in the photosphere, we have implemented mathematical models to reconstruct the global coronal magnetic field of the Sun and simulate the evolution of the ambient solar wind flow from the Sun to the Earth. The comparison of our model results with in situ measurements has shown that our models give a realistic insight into the solar wind conditions at Earth. Using the implemented framework, we developed innovative ideas to optimize the transition between models of the corona and models for evolving the solar wind conditions near the Sun to Earth. These results are highly relevant, not only for research areas related to the evolving ambient solar wind but also for forecast centres such as NOAA (USA) and Met Office (UK). During the return phase, we used the developed models and the acquired expertise to investigate the influence of the solar wind on the propagation of coronal mass ejections (CMEs). In addition to our research activities, we have established two international research groups dedicated to tackling important challenges in modeling and predicting the ambient solar wind. In this internationally coordinated collaboration, we strive to serve the community and drive innovation in space weather research.