Combining Broadband Irradiance Measurements and Plasma Temperature
Approximations to Generate Solar EUV Spectra
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 profound
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 the MAVEN 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. We use the broadband EUVM measurements to
estimate Active Region temperature. This will allow us to select from a
library of AR reference spectra with different temperatures. We also
investigate how the prevalence of solar minimum coronal holes affects
our measurements and how to account for them. We present this updated
SynRef model to more accurately characterize the Solar EUV and soft
x-ray spectra.