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    SWAN observations of activity on the far side of the Sun

    Date: 19 Nov 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: 11 Jul 2005

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    • SWAN observes fading sunspots on the back side of the Sun

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