A new view of the Sun: highlights and insights from the SOHO Mission

Abstract

Since its launch in 1995, the Solar and Heliospheric Observatory (SOHO) has been revolutionizing our understanding of the Sun. In particular, major advances have been made in revealing the complex and very dynamic nature of the star's outer atmosphere or corona. Through optical, ultraviolet and extreme ultraviolet imagers and spectrometers, SOHO has provided an unparalleled breadth and depth of observational data of this portion of the Sun. This magnetically dominant plasma environment demonstrates numerous magnetic field/plasma interactions over a wide range of lengthscales and timescales. This review outlines how the instruments onboard SOHO diagnose the coronal plasma over an extensive wavelength range. Through high-resolution images and movies, this mission has revealed how the Sun's magnetic field structures the plasma (to form, for example, loops and tornadoes) and how instabilities trigger energy release on incredible scales (from coronal mass ejections). Current thinking on how the corona maintains its temperature in excess of two million degrees is presented. Complementary images from other space-based solar missions (Yohkoh and TRACE) are used to provide further examples of the above. Also, building upon the success of SOHO, future space-based solar missions are profiled.