09:15 〜 09:30
[MGI35-02] 黒点形成・進化に伴う太陽フレアの磁気流体シミュレーション
キーワード：黒点、フレア、磁気流体シミュレーション
Solar flares and coronal mass ejections (CMEs) are caused by a release of magnetic energy in the solar atmosphere. Large flares and CMEs have a potential impact on modern society depending on technologies. Superflares and CMEs have also been found in the other Sun-like stars, suggesting an impact on the habitability of exoplanets. It is important for space weather and stellar physics to reveal how large energy can be released by a single flare or CME. The sun is the only star that we can observe the photospheric magnetic fields and various kinds of magnetic activities in detail.
To estimate the possible energy release, we need to comprehend the evolution of magnetic fields from the solar interior (convection zone) to the upper plasma atmosphere (corona). In the observations, large flares are likely to occur in delta spots (one type of sunspots). Recent radiative MHD simulations revealed that the delta spots can be formed when the magnetic fluxes are transported from much deeper convection zone to the photosphere. The remained issue is to reveal the reason why the delta spots tend to cause large flares in the corona.
In this study, we investigated the evolution of coronal magnetic fields using zero-beta MHD simulations. We introduced the numerical data of the delta spot simulation into bottom boundary of the corona simulation. As a result, a large flare corresponding to M-class in the observations was reproduced. We also performed parameter survey on the ratio between toroidal and poloidal components of the initial flux ropes in the convection zone and spatial resolution as well. We found that, in the case of high spatial resolution, the released energy was larger. The onset of flare seemed to be random: we were not able to find out clear relationship between the tested parameters and the onset of flares. This result might be due to randomness of the turbulent flows in the photosphere. We need to perform further parameter surveys covering a sufficiently broad range of parameters to take ensemble.
To estimate the possible energy release, we need to comprehend the evolution of magnetic fields from the solar interior (convection zone) to the upper plasma atmosphere (corona). In the observations, large flares are likely to occur in delta spots (one type of sunspots). Recent radiative MHD simulations revealed that the delta spots can be formed when the magnetic fluxes are transported from much deeper convection zone to the photosphere. The remained issue is to reveal the reason why the delta spots tend to cause large flares in the corona.
In this study, we investigated the evolution of coronal magnetic fields using zero-beta MHD simulations. We introduced the numerical data of the delta spot simulation into bottom boundary of the corona simulation. As a result, a large flare corresponding to M-class in the observations was reproduced. We also performed parameter survey on the ratio between toroidal and poloidal components of the initial flux ropes in the convection zone and spatial resolution as well. We found that, in the case of high spatial resolution, the released energy was larger. The onset of flare seemed to be random: we were not able to find out clear relationship between the tested parameters and the onset of flares. This result might be due to randomness of the turbulent flows in the photosphere. We need to perform further parameter surveys covering a sufficiently broad range of parameters to take ensemble.