Four Years of SOHO Discoveries - Some Highlights
Publication date: 01 May 2000
Authors: Fleck, B., et al.
Journal: ESA Bulletin
Copyright: ESASince its launch on 2 December 1995, the Solar and Heliospheric Observatory (SOHO) has provided an unparalleled breadth and depth of information about the Sun, from its interior, through the hot and dynamic atmosphere, out to the solar wind. Analysis of the helioseismology data from SOHO has shed new light on a number of structural and dynamic phenomena in the solar interior, such as the absence of differential rotation in the radiative zone, subsurface zonal and meridional flows, sub-convection-zone mixing, a possible circumpolar jet, and very slow polar rotation. The ultraviolet imagers and spectrometers have revealed an extremely dynamic solar atmosphere in which plasma flows play an important role. Evidence for an upward transfer of magnetic energy from the Sun's surface toward the corona has been found. Electrons in coronal holes have been found to be relatively 'cool', whereas heavy ions are extremely hot and have highly anisotropic velocity distributions. The source region for the high-speed solar wind has been identified and the acceleration profiles of both the slow and fast solar wind have been measured.