Modeling Solar Spectral Irradiance (SSI) from Iron lines using the COronal DEnsity and Temperature (CODET) model version 1.1

Abstract

The COronal DEnsity and Temperature (CODET) model is a physics-based model (Rodr\'iguez-G\'omez et al. 2018; Rodr\'iguez-G\'omez 2017) . This model uses the relationship between the magnetic field, density, temperature, and EUV emission. This model provides mean daily Solar Spectral Irradiance time series in EUV wavelengths in long time scales from days to solar cycles. The current manuscript presents the updated/new CODET model version 1.1. It uses observational datasets from SDO/EVE MEGS-A at $28.4 \ \mathrm{nm}$ and $21.1 \ \mathrm{nm}$ wavelengths to obtain the goodness-of-fit between them and the modeled SSI from April 30, 2010, to May 26, 2014. The model described well observational data during that period, with less than $20\%$ error in both wavelengths. Additionally, SSI predictions are provided using the new model parameters from July 1996 to October 2024, where SOHO/MDI and SDO/HMI photospheric magnetic field data are available. These predictions were compared with GOES/EUVS at $28.4 \ \mathrm{nm}$ and mean daily values of SDO/AIA at $21.1 \ \mathrm{nm}$ data, with errors of $\sim 26\%$ and $42\%$ for $28.4 \ \mathrm{nm}$ and $21.1 \ \mathrm{nm}$, respectively. The error analysis for model fitting and predictions shows how accurate the model predictions are. Thus, the CODET model provides a reliable estimate of the Solar Spectral Irradiance time series in EUV wavelengths where no observational data is available, e.g., after the SDO/EVE MEGS-A era.