Modeling of the Solar Spectral Irradiance and its Variability
Alexander Shapiro [alexander.shapiro@pmodwrc.ch], Werner Schmutz, and Gaël
Cessateur; Physikalisch-Meteorologishes Observatorium Davos (PMOD/WRC),
Switzerland
We present spectral solar irradiance data from two recent European missions
PROBA-2 with LYRA radiometer onboard and PICARD with PREMOS package
onboard. The instruments cover together the solar spectrum from the EUV to nearinfrared. We provide a comparison with the VIRGO/SOHO and
SOLSTICE+SIM/SORCE data.
The recently developed and published COde for Solar Irradiance (COSI) is
employed to model the observed variability of the solar irradiance. The modeling is
used to test and constrain the existing models of the solar atmosphere, e.g., the
temperature structure of the photosphere and the treatment of the pseudo-continuum
opacities in the Herzberg continuum range.
We discuss the long-term solar variability and outline an observational program
which can help to constrain the estimations of the secular trend in the solar irradiance.
The comparison of the reconstructed solar irradiance with the stellar photometric
records allows us to addresses the question of whether the Sun is a typical star or an
outlier among its stellar cohort.