X-ray and EUV observations of large-scale coronal structures

Large-scale coronal streamers, first recognized in solar eclipse images and in white-light coronagraph data, are now more frequently observed with space-borne coronagraphs e.g. LASCO on SOHO, out to a distance of similar to 30R circle dot. The SOHO spectrometers, CDS and SUMER, have been used for emission line intensity studies of these structures. The SOHO UVCS has undertaken UV spectroscopy and visible polarimetry studies of the corona to a height of similar to 12R circle dot. Yohkoh SXT observations of large coronal structures, made in the period before December 1992, will be discussed. Subsequent observations by the SOHO instruments will also be reviewed. The origin of the slow solar wind will be discussed. The properties of transequatorial loop systems will be reviewed and their relationship to coronal heating, CME occurrence and flaring examined. Recent work on the relationship between solar coronal and stellar X-ray radiance and unsigned magnetic flux will be briefly described.