Finding the origin of the slow solar wind
The origins and release mechanisms of stellar winds are long-lasting open challenges in astrophysics. Stellar winds play a fundamental role in the long-term evolution of stars and the habitability of their orbiting planets.  In the solar case, the wind is observed in at least two states, fast and slow winds, that differ in their bulk properties and composition, pointing to different coronal origins. A theoretical explanation for the slow wind must explain both its variable bulk properties and its peculiar composition. This includes the measured high charge states of minor ions, the abundance variation of Helium during the solar cycle and the high abundance of elements with low first ionisation potential (so called FIP effect) reaching four times the photospheric abundance. SLOW_SOURCE is a comprehensive research project that will use current and upcoming observations as well as completely novel models of the solar atmosphere to determine the origin of the slow wind. We will develop plasma transport models coupling major and all known important minor constituents along realistic coronal magnetic field lines. This model will be the first of its kind producing modelled observations (spectroscopy, imagery) and expected in situ signatures directly from the modelled minor constituents.  Combined with data from space and ground-based observatories, our new multi-species, multi-temperature 3-dimensional modelling of coronal plasma will provide new ways to infer the properties of stellar winds and tools to study the fundamental transport and heating processes of stellar plasmas. Determining the enigmatic release mechanism(s) of the slow solar wind constitutes a key objective of the upcoming Parker Solar Probe mission that will obtain radically new observations right from the start of the project. The project (2019-2024) will also be an excellent preparation for the Solar Orbiter mission that should obtain its first data during the second half of the project (2022-2024).