The Ultraviolet Sun

The Ultraviolet Sun

. This composite image, taken by two SOHO instruments and joined at the black circle, reveals the ultraviolet light of the Sunís atmosphere from the base of the corona to millions of kilometers above the visible solar disk. The region outside the black circle, obtained by UVCS, shines in the ultraviolet light emitted by oxygen ions flowing away from the Sun to form the solar wind. The inner image, obtained by EIT, shows the ultraviolet light emitted by iron ions at a temperature near two million degrees Kelvin. Dark areas, called coronal holes, are found at both poles of the Sun (top and bottom) and across the disk of the Sun; they are the places where the highest-speed solar wind originates. The structure of the corona is controlled by the Sunís magnetic field which forms the bright active regions on the solar disk and the ray-like structures extending from the coronal holes. [Courtesy of the SOHO UVCS consortium (outer region) and the SOHO EIT consortium (inner region). SOHO is a project of international cooperation between ESA and NASA.]

Copyright 2010, Professor Kenneth R. Lang, Tufts University