Characterizing Spectroscopy of Small to Large Solar Flares with Fermi GBM

The Fermi Gamma-ray Burst Monitor (GBM) is a high energy astrophysics instrument that has been in operation since 2009. GBM has observed thousands of solar flares. This set of observations offers many benefits to the solar physics community including: observation of flares not observed by RHESSI, observations after the decommissioning of RHESSI, full-Sun spectroscopy with time bins of 1/16^th second, and coincident observations with many other observatories including SDO, RHESSI, and Solar Orbiter, among others. However, there are limitations to solar spectroscopy using GBM data as a result of it being optimized for the observation of gamma-ray bursts, which exhibit lower count rates than solar flares. This work aims to provide a robust and comprehensive characterization of GBM solar spectroscopy by making comparisons with RHESSI. It also utilizes a pulse pile-up model created by Chaplin et al (2013), applying it toward solar flare spectra for the first time. Preliminary results indicate that GBM achieves agreement with RHESSI for solar flares where pulse pile-up is minor, however the pile-up model is inadequate for large flares. Agreement between RHESSI and GBM is achievable for nonthermal spectral parameters, but it is challenging to achieve agreement for the parameters of thermal flare plasma, even with application of a pulse pile-up model.