Solar Orbiter Investigations of Solar Wind in Corona.

Abstract:

The study of the dynamics of the solar coronal plasma, continuously flowing outwards and from time to time suddenly ejected in transient events, is one of the key objectives of the future space missions dedicated to heliophysics. In the last decades, the SOHO coronagraphs obtained the first measurements of the velocity and acceleration of the solar wind at coronal heights by means of spectroscopic techniques and by tracking the motion of coronal tracers, such as coronal blobs. The Solar Orbiter coronagraph, Metis, has been designed to further extend the investigation of coronal expansion in order to monitor at high temporal and spatial resolution the dynamic conditions of the full corona as they evolve on different time-scales and to identify wind streams with different characteristics. Coronal outflow maps are derived by combining the simultaneous images of the corona obtained in the visible and in the resonantly scattered ultraviolet light in order to measure the Doppler dimming of the UV emission, which is function of the plasma outward speed. In addition, during the spacecraft out of ecliptic observations in the late phase of the mission, the Solar Orbiter instruments will allow us to observe the velocity of the nascent fast wind at the poles and to assess the longitudinal extent of wind streams and coronal mass ejections in their propagation through the corona.