11:45 AM - 12:00 PM
[PEM11-14] Development of a large-flare warning system based on the κ-scheme : correlation between flare index and high free energy region
Keywords:Space Weather, Prediction, Solar Flare, Solar magnetic field
NICT provides space weather forecast and predicts the largest solar flare which is expected to occur within 24 hours. We announce the urgent solar flare alert right “after” the large flare occurred. However, it does not sometimes work to prevent geoeffective incidents (e.g., Dellinger phenomena), because the electromagnetic waves immediately reach to Earth from the Sun. It is thus required to develop the large flare warning system that predicts and notices large flare occurrence at least a few hours “before” its onset. Recently, a new large flare prediction model “κ-scheme” was developed by Kusano et al. 2020. In the κ-scheme, the critical condition of large flare occurrence is quantitatively described based on the double-arc instability theory (Ishiguro & Kusano 2017).
We develop an X-class flare warning system based on the κ-scheme, in order to practically use in our space weather forecast operation. We first extrapolate the three-dimensional coronal magnetic field (nonlinear force-free field; NLFFF) in an active region from the photospheric magnetic field data obtained by SDO. We then calculated the following parameters based on the NLFFF: High Free Energy Region (HiFER) where the strong magnetic free energy is stored, the critical radius rc for magnetic reconnection to trigger the double-arc instability, and the estimated minimum energy Er that can be released by the double-arc instability. Kusano et al. 2020 suggests that flares larger than X2-class occur under the condition of rc < 1 [Mm], Er > 4x1031 [erg]. We are planning to issue an advisories and/or alerts for an imminent X-class flare based on the HiFER together with the rc, and Er conditions.
In the process of the X-class flare warning system development, we provide an online viewer of HiFERs to NICT space weather operation. We can easily check HiFERs in each active regions on the solar disk as well as stored energy in each HiFER in near real time by the viewer. The NLFFF extrapolation is mandatory to obtain "releasable energy" in the active region, but it needs huge calculation resources. On the other hand, we can easily calculate "stored energy" in HiFERs using only vector magnetic field data of active regions. It is useful for flare forecasting if there is a correlation between flare index and stored energy in HiFERs. We thus investigated the correlation and report the progress.
We develop an X-class flare warning system based on the κ-scheme, in order to practically use in our space weather forecast operation. We first extrapolate the three-dimensional coronal magnetic field (nonlinear force-free field; NLFFF) in an active region from the photospheric magnetic field data obtained by SDO. We then calculated the following parameters based on the NLFFF: High Free Energy Region (HiFER) where the strong magnetic free energy is stored, the critical radius rc for magnetic reconnection to trigger the double-arc instability, and the estimated minimum energy Er that can be released by the double-arc instability. Kusano et al. 2020 suggests that flares larger than X2-class occur under the condition of rc < 1 [Mm], Er > 4x1031 [erg]. We are planning to issue an advisories and/or alerts for an imminent X-class flare based on the HiFER together with the rc, and Er conditions.
In the process of the X-class flare warning system development, we provide an online viewer of HiFERs to NICT space weather operation. We can easily check HiFERs in each active regions on the solar disk as well as stored energy in each HiFER in near real time by the viewer. The NLFFF extrapolation is mandatory to obtain "releasable energy" in the active region, but it needs huge calculation resources. On the other hand, we can easily calculate "stored energy" in HiFERs using only vector magnetic field data of active regions. It is useful for flare forecasting if there is a correlation between flare index and stored energy in HiFERs. We thus investigated the correlation and report the progress.