Exploring the Solar Wind from Its Source on the Corona into the Inner Heliosphere during the First Solar Orbiter–Parker Solar Probe Quadrature

International audienceThis Letter addresses thefirst Solar Orbiter(SO)–Parker Solar Probe(PSP)quadrature, occurring on 2021 January18 to investigate the evolution of solar wind from the extended corona to the inner heliosphere. Assuming ballisticpropagation, the same plasma volume observed remotely in the corona at altitudes between 3.5 and 6.3 solar radiiabove the solar limb with the Metis coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing thelocal properties of the solar wind to be linked to the coronal source region from where it originated. Thanks to theclose approach of PSP to the Sun and the simultaneous Metis observation of the solar corona, theflow-alignedmagneticfield and the bulk kinetic energyflux density can be empirically inferred along the coronal current sheetwith an unprecedented accuracy, allowing in particular estimation of the Alfvén radius at 8.7 solar radii during thetime of this event. This is thus the veryfirst study of the same solar wind plasma as it expands from the sub-Alfvénic solar corona to just above the Alfvén surfac