Abstract
Soft x-ray and EUV radiation from the Sun is absorbed by and ionizes the
atmosphere, creating both the ionosphere and thermosphere. Temporal
changes in irradiance energy and spectral distribution can have drastic
impacts on the ionosphere, impacting technologies such as satellite drag
and radio communication. Because of this, it is necessary to estimate
and predict changes in Solar EUV spectral irradiance. Ideally, this
would be done by direct measurement but the high cost of solar EUV
spectrographs makes this prohibitively expensive. Instead, scientists
must use data driven models to predict the solar spectrum for a given
irradiance measurement. In this study, we further develop the Synthetic
Reference Spectral Irradiance Model (SynRef). The SynRef model, which
uses broadband EUV irradiance data from EUVM at Mars, was created to
mirror the SORCE XPS model which uses data from the TIMED SEE instrument
and the SORCE XPS instrument at Earth. Both models superpose theoretical
Active Region and Quiet Sun spectra generated by CHIANTI to match daily
measured irradiance data, and output a modeled solar EUV spectrum for
that day. By adjusting the weighting of Active Region and Quiet Sun
spectra, we update the SynRef model to better agree with the FISM model
and with spectral data collected from sounding rocket flights. We also
use the broadband EUVM measurements to estimate AR temperature. This
will allow us to select from a library of AR reference spectra with
different temperatures. We present this updated SynRef model to more
accurately characterize the Solar EUV and soft x-ray spectra.