Investigating the physics of the solar wind and its origin at the Sun using Solar Orbiter and Parker Solar Probe

As it orbits the Sun, the Earth is constantly buffeted by highly energetic charged particles; a phenomenon known as the solar wind. This constant outflow of material originates in coronal holes, regions of the solar atmosphere (the corona) which appear dark in extreme ultraviolet and X-ray observations of the Sun. Although it is produced regardless of solar activity and is a key driver of space weather, a phenomenon which can adversely affect spacecraft and the near-Earth environment, the origins and evolution of the solar wind and its relationship to coronal holes are very poorly understood. Coronal holes are very quiet, stable, long-lived features that can cover significant fractions of the solar surface, that have been under-investigated by the wider solar physics community in favour of more active phenomena. As a result, there are many significant open questions regarding the formation and evolution of coronal holes, including why they appear dark in some wavelengths (e.g., EUV and X-ray) but bright in others (e.g., Lyman-alpha), and how their boundaries evolve and interact with neighbouring quiet Sun regions. These questions have significant implications for space weather research and forecasting, and answering them will improve our ability to mitigate against the effects of space weather on space-based and ground-based infrastructure.

The recent launch of the Parker Solar Probe and Solar Orbiter spacecraft promises to help shed some light on these issues. Both spacecraft are travelling closer to the Sun than ever before, carrying a variety of remote-sensing and in-situ instrumentation designed to observe the Sun with very high resolution and probe the solar wind before it is mixed up on its journey through the solar system. The aim of this project is to use these new observatories to investigate coronal holes at higher spatial and temporal scales than before, quantifying their evolution and interaction with the surrounding quiet Sun, and measuring how this continuous interaction affects the solar wind released into the solar system. The project will involve working closely with several of the teams at UCL who have instruments onboard Solar Orbiter, including the Extreme Ultraviolet Imager and Solar Wind Analyser, as well as with scientists involved in space weather forecasting and prediction.