Validation of computed extreme ultraviolet emission spectra during solar flares

Shohei Nishimoto,Shinsuke Imada,Toshiki Kawai,Tomoko Kawate,Kyoko Watanabe

doi:10.1186/s40623-021-01402-7

Abstract

X-rays and extreme ultraviolet (EUV) emissions from solar flares rapidly change the physical composition of the Earth’s thermosphere and ionosphere, thereby causing space weather phenomena such as communication failures. Numerous empirical and physical models have been developed to estimate the effects of flare emissions on the Earth’s upper atmosphere. We verified the reproduction of the flare emission spectra using a one-dimensional hydrodynamic calculation and the CHIANTI atomic database. To validate the proposed model, we used the observed EUV spectra obtained by the Extreme ultraviolet variability experiment (EVE) on board the Solar Dynamics Observatory (SDO). We examined the “EUV flare time-integrated irradiance” and “EUV flare line rise time” of the EUV emissions for 21 events by comparing the calculation results of the proposed model and observed EUV spectral data. The proposed model successfully reproduced the EUV flare time-integrated irradiance of the Fe VIII 131 Å, Fe XVIII 94 Å, and Fe XX133 Å, as well as the 55–355 Å and 55–135 Å bands. For the EUV flare line rise time, there was an acceptable correlation between the proposed model estimations and observations for all Fe flare emission lines. These results demonstrate that the proposed model can reproduce the EUV flare emission spectra from the emitting plasma with a relatively high formation temperature. This indicates that the physics-based model is effective for the accurate reproduction of the EUV spectral irradiance.

Highlights

To consider outer space as a place for deploying advanced space activities, a common fundamental system, called space infrastructure, is required
We present the statistical results of the extreme ultraviolet (EUV) emission spectra observed by Solar Dynamics Observatory (SDO)/Extreme ultraviolet variability experiment (EVE) for 21 flare events and compare these with the spectra reproduced by Kawai et al (2020)
We used Flare Emission Spectral Model (FISM) to compare with the proposed model; it should be noted that the FISM2 was released quite recently (Chamberlin et al 2020)

Summary

Introduction

To consider outer space as a place for deploying advanced space activities, a common fundamental system, called space infrastructure, is required. Kawai et al (2020) introduced a new method for reproducing EUV flare emission spectra by considering the time evolution of the plasma distribution in the flare loop This method was constructed using a one-dimensional hydrodynamic calculation and an atomic database.

Statistical study for comparison between model and observation

Discussion and summary