Statistical and Observational Research on Solar Flare EUV Spectra and Geometrical Features

Abstract

We performed statistical analysis on the flare emission data to examine parameters related to the flare extreme-ultraviolet (EUV) spectra. This study used the data from the Geostationary Operational Environmental Satellite X-ray Sensors to determine the fundamental flare parameters. The relationship between soft X-ray data and EUV emission data observed by the Extreme Ultraviolet Variability Experiment on board the Solar Dynamics Observatory (SDO) MEGS-A was investigated for 50 events. The results showed the hotter Fe line emissions have strong correlation with soft X-ray data in many cases. However, our statistical study revealed that EUV flare peak flux of Fe xv, Fe xvi and He ii lines have weak correlation with soft X-ray peak flux. In EUV line light curves, there was time difference in peak time, however the tendency to reach the peak in order from the hotter line to cooler line was not so clear. These results indicate that the temporal evolution of EUV emission can be roughly explained by soft X-ray data. However, the time changes of temperature and density distributions in the flare loop must be needed for accurate reproduction. Moreover, we compared the geometrical features of solar flares observed by the Atmospheric Imaging Assembly on board the SDO with the fundamental flare parameters for 32 events. The ribbon distance strongly correlated with both soft X-ray flare rise and decay times. This results indicate that the geometrical feature is essential parameter for predicting flare emission duration.

PSTEP: project for solar–terrestrial environment prediction

“…To find out the parameters that control the properties of flare emission, a statistical analysis on the observed flare emission data was performed to examine flare parameters related to the flare EUV spectra. From this study, it was found that the geometrical features of flare, such as flare loop length and ribbon distance, were found to be essential parameters for predicting flare emission duration (Nishimoto et al 2020).…”

Multiwavelength Sun-as-a-star Analysis of the M8.7 Flare on 2022 October 2 Using Hα and EUV Spectra Taken by SMART/SDDI and SDO/EVE

“…The Doppler signals in Sun-as-a-star spectra are also analyzed using the EUV spectral lines taken by the Extreme ultraviolet Variability Experiment (EVE; Woods et al 2012) on board the Solar Dynamics Observatory (SDO; Pesnell et al 2012). SDO/EVE has been mainly used for analyzing a light curve of each EUV line (e.g., Harra et al 2016;Nishimoto et al 2020). Furthermore, many recent studies have firmly established the capability of Doppler analysis for solar active phenomena by SDO/EVE (Hudson et al 2011(Hudson et al , 2022Chamberlin 2016;Cheng et al 2019;Xu et al 2022;Fitzpatrick & Hudson 2023;Lu et al 2023).…”