Nowcast of an EUV dynamic spectrum during solar flares

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

doi:10.1016/j.jastp.2020.105302

Cited by 12 publications

(28 citation statements)

References 40 publications

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“…Finally, we derived the EUV emission spectra in all wavelengths that was comparable to the observation (see the Fig. 1 in Kawai et al (2020)).…”

Section: Conversion From Goes X-ray To Euv Spectrummentioning

confidence: 59%

“…These studies used a zero-dimensional hydrodynamic model to simulate the thermal evolution of the coronal loops, called the enthalpy-based thermal evolution of loops (EBTEL) model, that could calculate the temperature and density in the flare loop without calculating the spatial loop evolution (Klimchuk et al 2008;Cargill et al 2012). The EBTEL model did not calculate the spatial distribution of the emitting plasma in the flare loop; hence, it is possible that the emission from the transition region plasma would not be reproduced accurately (Kawai et al 2020). Kawai et al (2020) introduced a new method for reproducing EUV flare emission spectra considering the time evolution of the plasma distribution in the flare loop.…”

Section: Introductionmentioning

confidence: 99%

“…The EBTEL model did not calculate the spatial distribution of the emitting plasma in the flare loop; hence, it is possible that the emission from the transition region plasma would not be reproduced accurately (Kawai et al 2020). Kawai et al (2020) introduced a new method for reproducing EUV flare emission spectra 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.…”

Section: Introductionmentioning

confidence: 99%

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Validation of Extreme Ultraviolet Emission Spectra During Solar Flares 

Nishimoto

Watanabe

Kawai

et al. 2020

Preprint

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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. To predict the effects of flare emissions on the Earth’s upper atmosphere, numerous empirical and physical models have been developed. We verify the extent of reproducing the flare emission spectra using a one-dimensional hydrodynamic calculation and the CHIANTI atomic database. To verify the proposed model, we use the observed EUV spectra obtained by the extreme ultraviolet variability (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 succeeded in reproducing the EUV flare time-integrated irradiance of the Fe VIII 131 Å, Fe XVIII 94 Å, and Fe XX 133 Å, as well as the 55 to 355 Å and 55 to 135 Å bands. For the EUV flare line rise time, there was 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 relatively high formation temperature. This indicates that the physics-based model is effective for the accurate reproduction of EUV spectral flux.

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“…Finally, we derived the EUV emission spectra in all wavelengths that was comparable to the observation (see the Fig. 1 in Kawai et al (2020)).…”

Section: Conversion From Goes X-ray To Euv Spectrummentioning

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Validation of Extreme Ultraviolet Emission Spectra During Solar Flares 

Nishimoto

Watanabe

Kawai

et al. 2020

Preprint

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“…However, SDO/EVE MEGS-A, which was observing 60-370 Å that has a large effect on the Earth's atmosphere, has not been observed due to a failure. Therefore, we estimated are emission spectrum by the method of Kawai et al (2020). [10] In our model, we assumed a semicircular are loop whose diameter is the distance between two are ribbons observed in this are, simulated the plasma motion in the are loop with 1D-hydro model.…”

Section: Observational Data and Modelsmentioning

confidence: 99%

“…[5] Therefore, in order to reproduce the observed are emission, we constructed new are emission model based on physical processes (Imada et al, 2015;Kawai et al, 2020). In our model, the physical process of the plasma in the are 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).…”

Section: Introductionmentioning

confidence: 99%

Model-based reproduction and validation of the total spectrum of solar flare and their impact on the global environment at the X9.3 event of September 6, 2017

Watanabe

Jin

Nishimoto

et al. 2020

Preprint

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We tried to reproduce the total electron content (TEC) variation in the Earth's atmosphere from the temporal variation of the solar flare spectrum of the X9.3 flare on September 6, 2017. The flare spectrum of the Flare Irradiance Spectral Model (FISM) which is most widely used and the flare spectrum from the 1D hydrodynamic model which considers the physics of plasma in the flare loop are used in the GAIA model which is a simulation model of the Earth's whole atmosphere and ionosphere, and calculate the difference of TEC. And then, we compared these results with the observed TEC. When we used the FISM flare spectrum, difference of TEC from the background was in a good agreement with the observation. On the other hand, when the flare spectrum of the 1D-hydro model was used, the result varied depending on the presence or absence of the background. This difference which depends on the models is thought to represent which EUV radiation is primarily responsible for increasing TEC. From the flare spectrum obtained from these models and the calculation result of TEC fluctuation using GAIA, it is considered that the enhancement in EUV emission about 15 to 35 nm is mainly contributes to increasing TEC rather than that of X-ray emission that has been thought to be mainly responsible for sudden ionospheric disturbance (SID). Also, from the altitude/wavelength distribution of the ionization rate of Earth's atmosphere by GAIA, it was found that EUV radiation of about 15–35 nm affects a wide altitude range of 120–300 km, and TEC enhancement is mainly caused by ionization of nitrogen molecules. (265 words)

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