Abstract


  EUV AND UV IRRADIANCE VARIABILITY AND SPATIALLY RESOLVED IMAGES

  R. Kariyappa, Indian Institute of Astrophysics, rkari@iiap.res.in
  J. Zender, ESA/ESTEC, joe.zender@esa.int
  L. Dame, CNRS/LATMOS,

The magnetic field plays a dominant role in the solar irradiance variability. Determining the contribution of various magnetic features to this variability is important in the context of heliospheric studies and Sun-Earth connection. We studied the solar irradiance variability and its association with the underlying magnetic field for a period of four years (January 2011 - January 2015). We used observations from the Large Yield Radiometer (LYRA), the Sun Watcher with Active Pixel System detector and Image Processing (SWAP) on board PROBA2, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The Spatial Possibilistic Clustering Algorithm (SPoCA) is applied on the EUV observations obtained from the AIA to segregate coronal features by creating segmentation maps of the Active Regions (ARs), the Coronal Holes (CHs) and the Quiet Sun (QS). Further, these maps are applied on the full-disk SWAP intensity images and the full-disk HMI line-of-sight (LOS) magnetograms to isolate the SWAP coronal features and photospheric magnetic counterparts, respectively. We then computed full-disk and feature-wise averages of EUV intensity and LOS magnetic flux density over ARs/CHs/QS. The variability in these quantities is compared with those of LYRA irradiance values. Variations in the quantities resulting from the segmentation, namely the integrated intensity and the total magnetic flux density of ARs/CHs/QS regions are compared with the LYRA irradiance variations. We find that the EUV intensity over ARs/CHs/QS is well correlated with the underlying magnetic field. In addition, variations in the full-disk integrated intensity and magnetic flux density values are correlated with the LYRA irradiance variations.