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YLA Soft X-ray Irradiances

Solar soft X-ray irradiance derived from Yohkoh/SXT full-sun images (SXT Level_2 data) in the YLA. Data were processed in the following steps:

  1. Image pair selection; The YLA level 2 data images were screened to remove those with telemetry loss, severe saturation due to flares and severe noise due to high energy particles, then made pairs of Al.1 and AlMg images obtained within 10 minutes difference.
  2. Collection of full-Sun signals; Sum up coronal intensities of the both filter images included in the area within 1.2Rs from the disk center. This image shows the sample of the Al.1 and AlMg filter images, in which the areas outside 1.2Rs from the disk center were masked.
  3. Derive filter-ratio temperatures and emission measures; Apply the filter-ratio technique to each Al.1 and AlMg signal pairs to obtain the full-Sun averaged temperatures (K) and volume emission measures (cm^-3).
  4. Isothermal coronal spectrum (lines and continuum) is calculated from the derived temperature and emission measure, using CHIANTI atomic DB and software (ver. 8.0). So-called 'hybrid' elemental abundances by Schmelts et al. (2012) is assumed in accordance with the assumption by SXT's default response functions.
  5. Integrate the obtained spectrum over (3-30Å) or other desired range (e.g. 1-8Å) to derive the radiant intensity of the coronal plasma, then converted to the irradiance at the distance of 1 AU in the unit of W/m^2.

Daily Averaged Data

Data from all avaiable image pairs

Full-sun integrated filter-ratio Te, EM, irraiance in 3-30 and 1-10Å wavelength range (yearly text file).

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