12:00 〜 12:15
[PEM11-15] Validation of electron density in the ionospheric D- and lower E-region during solar flares using PHITS and GAIA models
キーワード：短波障害、デリンジャー現象、太陽フレア、電離圏
Short-wave fadeout (SWF) occurs when the electron density in the ionospheric D- and lower E-region increases rapidly in a short period, mainly due to X-ray emission during solar flares. It is necessary to accurately understand the electron density variation in the ionosphere to estimate the magnitudes of SWFs. The GAIA (Jin et al., 2011) is one of the effective numerical simulation models for the whole global atmosphere, which can provide electron density variations throughout the ionosphere in solar flare emissions. However, it still does not account for photochemical reactions in the ionosphere below 100 km.
The PHITS code (Sato et al., 2023), a particle transport and collision simulation code using the Monte Carlo method, was used to reproduce the electron density in the ionospheric D- and lower E-region due to flare X-ray emission. We input the GOES X-ray data into PHITS and simulated the altitude distribution of the ionization rate (q). We used the effective recombination coefficient (αeff) given by Gledhill (1986) and derived the electron density (ne) from ne2 =q/αeff.
The ionosonde provides the electron density in the bottomside ionosphere. The variation of minimum frequency in the ionogram (fmin) during solar flares mainly corresponds to the electron density variations in the ionospheric D- and lower E-region. We simulated fmin value using the electron density from the PHITS and GAIA. We compared their simulated fmin with observed fmin to validate the simulated electron density. We also compared the simulated electron density with the observed electron density. The linear correlation coefficient between the simulated and observed fmin values has a good correlation. The ratio of the number of simulated blackouts correctly to the total number of blackouts was ~70%. We found that PHITS might reproduce the electron density in the ionospheric D- and lower E-region at the peak time of flare and estimated the magnitudes of SWFs. In this presentation, we will discuss the validation of electron density variations using PHITS in detail.
The PHITS code (Sato et al., 2023), a particle transport and collision simulation code using the Monte Carlo method, was used to reproduce the electron density in the ionospheric D- and lower E-region due to flare X-ray emission. We input the GOES X-ray data into PHITS and simulated the altitude distribution of the ionization rate (q). We used the effective recombination coefficient (αeff) given by Gledhill (1986) and derived the electron density (ne) from ne2 =q/αeff.
The ionosonde provides the electron density in the bottomside ionosphere. The variation of minimum frequency in the ionogram (fmin) during solar flares mainly corresponds to the electron density variations in the ionospheric D- and lower E-region. We simulated fmin value using the electron density from the PHITS and GAIA. We compared their simulated fmin with observed fmin to validate the simulated electron density. We also compared the simulated electron density with the observed electron density. The linear correlation coefficient between the simulated and observed fmin values has a good correlation. The ratio of the number of simulated blackouts correctly to the total number of blackouts was ~70%. We found that PHITS might reproduce the electron density in the ionospheric D- and lower E-region at the peak time of flare and estimated the magnitudes of SWFs. In this presentation, we will discuss the validation of electron density variations using PHITS in detail.