Iron Fluorescence in X-class Solar Flares: Aditya-L1/SoLEXS Observations

The iron fluorescence produced by the irradiation of the photosphere by coronal X-rays is a powerful diagnostic of flare geometry. This study presents the first comprehensive analysis of Fe Kα characteristics in 47 X-class flares observed during the inaugural year of the Solar Low Energy X-ray Spectrometer (SoLEXS) on board India’s Aditya-L1 mission. Leveraging SoLEXS’s capability for simultaneous broadband continuum and line measurements, the Fe Kα flux and the exciting continuum flux (F>7.11 keV) are quantified for each event. Our results confirm the center-to-limb dependence of the fluorescence efficiency, consistent with theoretical models. These findings demonstrate that modern silicon drift detectors, despite having lower spectral resolution than traditional crystal spectrometers, provide a new diagnostic for the iron fluorescence observations.