SWAN observations of activity on the far side of the Sun
Date: 18 November 2003
Depicts: MgII solar index deduced from SWAN data
Copyright: ESA. Credit: Jean-Loup Bertaux and Eric Quemerais at Service d'Aéronomie du CNRS
Solid line: Time variation of the MgII solar index as seen by a virtual observer, rotating with the Sun, and always facing the region of the Sun which was facing the Earth on 28 October 2003, when a very active region including two sunspots was visible. This variation was deduced from the SWAN full sky images in the light of Lyman-alpha, produced by the illumination by the Sun of hydrogen atoms in the solar system.
The MgII index is a direct index of the solar activity, and the strong decrease observed between November 7 and November 17 is a sign of the fading activity of the two sunspots.
Dotted line: Time variation of the MgII solar index as seen from the Earth for the same time period.
Last Update: 1 September 2019