Towards a Physics-Based Flare Irradiance Model

The Extreme UltraViolet (EUV) irradiance from solar flares is a critical driver of short term variability in the Earth's upper atmosphere. The EUV Variability Experiment (EVE) onboard NASA's Solar Dynamics Observatory (SDO) has been making moderate spectral resolution (0.1 nm), high time cadence (10 s) measurements of the solar EUV irradiance (5-105 nm) since 2010. A key observation from EVE is that flares of the same magnitude at one wavelength (e.g. GOES XRS) have different peak intensities and time profiles in other wavelengths. As it is impractical to measure the entire EUV spectrum with sufficient spectral resolution and temporal cadence to capture these differences for space weather operations, the next generation of flare irradiance models must be able to capture these variations.

We have developed a framework for a physics-based flare irradiance model based on the EBTEL model. At present, this Multi-Strand Flare Irradiance Model (MS-FIM) is able to predict EUV lightcurves over a range of coronal temperatures given the lightcurves from two EVE lines as inputs.

In this paper, we present an overview of the Multi-Strand Flare Irradiance Model as well as initial results showing its ability to predict the irradiances for a diverse range of flares, including EUV late phase flares. We also describe preliminary efforts to drive the model with parameters derived from images of the flaring region instead of EUV lightcurves.