The Solar Wind

The solar corona produces a continuous outflow of plasma influencing the entire solar system and beyond to over a hundred of astronomical units. Due to the Sun's proximity the source regions of that wind can be observed remotely with great precision and the escaping plasma can be measured directly in situ. Space missions launched over the past six decades have exploited this fantastic plasma laboratory to reveal the very rich physical processes at play as the solar wind forms and expands into space. This chapter provides a brief synthesis of these observational discoveries. It covers a broad range of topics, from the large-scale imaging and detailed spectroscopic observations of the wind source regions to the dynamical evolution of interplanetary plasma down to kinetic scales. Despite the great advances accomplished in solar wind research over the past decades, many mysteries remain concerning the origins of the solar winds. These mysteries are currently being addressed with a new fleet of extraordinary missions en route to our star.