A new view of coronal structures: implications for the source and acceleration of the solar wind

We show how the complement of white light and a suite of Fe coronal forbidden line images taken during total solar eclipses since 2006 have yielded new insights into the physical properties of the coronal plasma and the role of the magnetic field. The unique properties of these spectral lines make them ideal diagnostic tools for exploring the first few solar radii above the photosphere where the expansion of the corona and the acceleration of the solar wind occur. In particular, these observations show how: (1) localized enhancements of the ion densities relative to electrons appear in some magnetic structures, (2) the transition between a collision-dominated to a collisionless plasma occurs within a heliocentric distance of 1.2 - 1.6 R_s, (3) the expanding corona is characterized by an electron temperature of 10^6 K, and (4) prominences are enshrouded by hot 2 × 10^6 K coronal plasma. We discuss the implications of these observations for the source and acceleration of the solar wind.