Title: Monitoring Solar Activity From SWAN/SOHO Lyman Alpha Interplanetary Background Images
Author: Quemerais Eric
Affil: Service d'Aeronomie du CNRS, Verrieres-le-Buisson, France
Email: eric.quemerais@aerov.jussieu.fr
Authors: Bertaux Jean-Loup, Lallement Rosine, Kyrola Erkki, Schmidt Walter
Affils: Finnish Meteorological Institute, Helsinki, Finland
Abstract: We present the results of a new method used to derive spatial and temporal variations of the H Lyman alpha flux emitted by the sun in all directions of space. This method uses the data obtained by the SWAN instrument on SOHO. We show how these maps of solar Lyman alpha flux distributions can be linked to the activity on the solar disk. Quite often, the activity is related to the presence on the surface of the sun of an active region which appears rather suddenly and may last for several months. These active regions are known to be brighter in Lyman alpha radiation than the quiet sun. Accordingly, they illuminate more interplanetary H atoms through resonance scattering. This excess of illumination related to active regions is clearly seen in full-sky Lyman alpha maps recorded by the Swan instrument on SOHO, including those excesses resulting from active regions which are on the far side of the Sun, i.e. not visible to solar disk imagers. We show how these maps can be used to predict the evolution of solar indices like the 10.7 cm flux or the MgII solar index. This technique could be used in the future to improve the quality of Space weather forecasting.