Temperature, Emission Measure, and Elemental Abundances of the Quiescent Sun from DAXSS Spectra

The study of the quiescent-Sun (non-flaring) periods and their plasma properties relative to flaring times is crucial for understanding solar activity and coronal heating. This analysis of Dual Aperture X-ray Solar Spectrometer (DAXSS) data uses soft X-ray (SXR) spectra obtained with 9-second cadence between 15:00:45 UTC to 16:02:12 UTC on 2022 September 21 (Day of Year 264). The analysis methods of using both f_vth.pro (IDL heritage code) and vvapec (Python code) to model DAXSS spectra of the quiescent Sun are described. Both methods create modeled X-ray emission spectra using input parameters of temperature (T), emission measure (EM), and elemental abundance factors (AF). By adjusting these parameters and comparing the modeled spectra with the observed DAXSS spectra, the best-fit values can be calculated providing information about the T and EM plasma properties and elemental composition of the quiescent-Sun active regions. It has been found that a model using 3 T, 3 EM, and separate AF for Mg, Si, S, Ca, and Fe is best to describe the averaged DAXSS quiescent-Sun spectrum. The three temperature components found were a cooler temperature of 2.3 MK, a moderate temperature of 4 MK, and a hotter temperature component of 9.1 MK. The abundances during this quiescent time were found to be mostly lower than the Feldman Standard Extended Coronal (FSEC) values, indicating that the sun is not exactly quiet, but also does not appear to be actively flaring. These values can be used to compare T, EM, and AF variations during active region evolution, solar flares, and the overall solar cycle. Additionally, the insights gained from this study can contribute to improving our understanding of coronal heating by providing insight into magnetic reconnection heating, such as from nano-flares during quiescent-sun periods.