Coronal spectroscopy: Probing sources of slow solar wind in active regions,and the early phases of solar flares

Coronal spectroscopy has pushed forward the understanding of physical processes in all phenomena on the Sun. In this review we concentrate specifically on plasma parameters measured in sources of the slow solar wind in active regions and the early phases of solar flares. These topics are a key part of the science goals of the Solar Orbiter mission (Müller et al., 2020) which has been designed to probe what drives the solar wind and solar transients that fill the heliosphere.Active regions, outside of flaring, have general characteristics that include closed loops showing red-shifted (down-flowing plasma), and the edges of the active regions showing blue-shifted (upflowing plasma). Constraining and understanding the evolution, behaviour and cause of the flows has been developed in the past years and are summarised. Of particular importance is the upflowing plasma which, in some cases, can contribute to the slow solar wind, and this review concentrates on recent results on this topic.The early phases of solar flares and their energy sources are not yet fully understood. For decades, there has been a huge interest in pin-pointing the trigger of a solar flare. Coronal spectroscopy has revealed small-scale dynamics that occurs tens of minutes before the flare begins. The understanding of the trigger is key to improving flare predictions in the future, as well as understanding the physical processes.Finally we look to the future of coronal spectroscopy, with new instruments and methodologies being developed that build on the current knowledge, and will improve significantly our physical understanding of processes at all scales on the Sun.