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

TL;DR

This study leverages the first Solar Orbiter-Parker Solar Probe quadrature to track solar wind from the corona to the inner heliosphere, providing unprecedented insights into its evolution and properties near the Alfvén surface.

Contribution

It is the first to empirically link coronal plasma observed remotely with in-situ measurements at 0.1 au during a quadrature, estimating the Alfvén radius with high accuracy.

Findings

Tracked solar wind from corona to 0.1 au

Estimated the Alfvén radius at 8.7 solar radii

Linked remote and in-situ plasma properties

Abstract

This Letter addresses the first Solar Orbiter (SO) -- Parker Solar Probe (PSP) quadrature, occurring on January 18, 2021, to investigate the evolution of solar wind from the extended corona to the inner heliosphere. Assuming ballistic propagation, the same plasma volume observed remotely in corona at altitudes between 3.5 and 6.3 solar radii above the solar limb with the Metis coronagraph on SO can be tracked to PSP, orbiting at 0.1 au, thus allowing the local properties of the solar wind to be linked to the coronal source region from where it originated. Thanks to the close approach of PSP to the Sun and the simultaneous Metis observation of the solar corona, the flow-aligned magnetic field and the bulk kinetic energy flux density can be empirically inferred along the coronal current sheet with an unprecedented accuracy, allowing in particular estimation of the Alfv\'en radius at 8.7 solar radii during the time of this event. This is thus the very first study of the same solar wind plasma as it expands from the sub-Alfv\'enic solar corona to just above the Alfv\'en surface.