Spectroscopic analysis of M and X class flares observed by SUNSTORM 1 XFM-CS

SUNSTORM 1 was a 2-unit CubeSat that observed hundreds of solar flares from low Earth orbit during its three-year operation between August 2021 and September 2024. Its payload was the X-ray Flux Monitor for CubeSats (XFM-CS), a non-imaging X-ray spectrometer capable of observing flares from A to X level in the 1–30 keV range with high precision. First results have demonstrated the instrument’s suitability for studies of larger solar eruption events. 

We construct an overview of M and X class flares observed by SUNSTORM 1/XFM-CS during the mission. The soft X-ray flare spectra are fitted with a thermal model to obtain the peak flux, peak count, emission measure and flare temperature. For eruptive events, flare characteristics are connected to properties of the accompanying coronal mass ejections, and links between key parameters are discussed in relation to the underlying mechanisms. Our study highlights the scientific output of the SUNSTORM 1 mission and provides spectroscopic results of some of the biggest flares observed during the rise phase of Solar Cycle 25.