Reproduction and validation of flare spectra and their impact on the global environment

Abstract:

It is well known that sudden increase of flare emissions accelerates the ionization and molecular dissociation of atmospheric components in the ionosphere and thermosphere, and it may cause the sudden ionospheric disturbance (SID). And then, communication failure also caused by the absorption of the short-wave by the SID is known as the Dellinger phenomenon (Dellinger 1937). In order to predict the occurrence of the Dellinger phenomenon, we must know the relationship with the flare emission which causes the Dellinger phenomenon. Therefore, in order to verify which wavelength of the solar flare spectrum influence the occurrence of the Dellinger phenomenon, we have developed a method to calculate the solar flare radiation spectrum and its effect on the Earth's atmosphere. For the flare emission, we constructed new model with physical processes (Imada et al. 2015, Kawai et al. 2020). In our model, the physical process of the plasma in the flare loop is reproduced by combining the one-dimensional hydrodynamic calculation using CANS (Coordinated Astronomical Numerical Software) 1D package with the CHIANTI atomic database (Dere et al. 2019). Then, in order to examine the effect of flare emission on the Earth’s atmosphere, we put our calculated flare spectra into the Earth's atmospheric model GAIA (Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy; Jin et al., 2011). Finally, we tried to reproduce the total electron content (TEC) variation for some flare events, then we compared calculated results with the observed TEC amount. Especially when we investigated about the X9.3 flare on September 6, 2017, it is considered that the EUV emission about 15-40 nm is mainly affected increasing TEC. This result was also confirmed from the altitude/wavelength distribution of the ionization rate of Earth's atmosphere by GAIA.