The existence of the hot corona is responsible for the existence of the solar wind. As the solar wind plasma escapes into interplanetary space it carries with it the solar magnetic field thus stretching it away from the Sun. To understand the physical processes that drive the solar wind and lead to the formation of two distinc states: the fast wind that can travel at more than 700 km/s, and the slow more variable wind that can coast at speeds as low as 300 km/s, one needs to understand the physical characteristics of the corona and the sources of the solar wind. The Solar Physics Group use spectroscopic observations of the corona acquired from the ground during total solar eclipses and from space, primarily from SOHO, the Solar Heliospheric Observatory, to explore the physical characteristics of the source regions of the solar wind. Through the study of the distribution of the plasma density in the corona, the Group found the surprising result that the solar wind expands from a much larger fraction of the solar surface than had been commonly believed for the past 30 years. Their analyis of earlier polarization measurements of coronal forbidden lines of iron led to the discovery that a large fraction of the magnetic field extends radially from the solar surface thus pointing to the possible existence of two sources of the magnetic field rooted at different depths in the solar interior. Observations made with the Ultraviolet Coronagraph Spectrometer (UVCS) on SOHO led to the first results showing that the slow solar wind in the inner corona originates in streamers, and that the transition from the fast to the slow wind produces a strong velocity shear within a few solar radii from the surface. The Group is currently preparing for total solar eclipse observations to be made from South Africa on December 4. They continue to pursue their research in exploring the hidden secrets of the Sun by tapping into the solar wind.


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