Flare Productivity of Major Flaring Solar Active Regions: A Time-Series Study of Photospheric Magnetic Properties
A solar active region (AR) that produces at least one M- or X-class major flare tends to produce multiple flares during its passage across the solar disk. It will be interesting to see if we can estimate how flare-productive a given major flaring AR is for a time interval of several days through investigating time series of its photospheric magnetic field properties. For this, we studied 93 major flaring ARs that were observed from 2010 to 2016 by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). More specifically, for each AR under study, the mean and fluctuation were calculated from an 8-day time series of each of 18 photospheric magnetic parameters extracted from the Space-weather HMI Active Region Patch (SHARP) vector magnetogram products at 12 min cadence. We then compared these with the AR 8-day flare index, which is defined as the sum of soft X-ray peak fluxes of flares produced in the AR during the same interval as the 8-day SHARP parameter time series. As a result, we found that the 8-day flare index is well correlated with the mean and/or fluctuation values of some magnetic parameters (with correlation coefficients of 0.6 – 0.7 in log–log space). Interestingly, the 8-day flare index shows a slightly better correlation with the fluctuation than the mean for the SHARP parameters associated with the surface integral of photospheric magnetic free energy density. We also discuss how the correlation varies if the 8-day flare index is compared with the mean or fluctuation calculated from an initial portion of the SHARP parameter time series.
KeywordsActive regions, magnetic fields Flares, relation to magnetic field
The authors would like to thank the anonymous referee for many constructive comments. This work was supported by the BK21 plus program through the National Research Foundation (NRF) funded by the Ministry of Education of Korea, the Basic Science Research Program through the NRF funded by the Ministry of Education (NRF-2016R1A2B4013131), NRF of Korea Grant funded by the Korean Government (NRF-2013M1A3A3A02042232), the Korea Astronomy and Space Science Institute under the R&D program supervised by the Ministry of Science, ICT and Future Planning, the Korea Astronomy and Space Science Institute under the R&D program ‘Development of a Solar Coronagraph on International Space Station (Project No. 2017-1-851-00)’ supervised by the Ministry of Science, ICT and Future Planning, and Institute for Information & communications Technology Promotion (IITP) grant funded by the Korea government (MSIP) (2018-0-01422, Study on analysis and prediction technique of solar flares). The data used in this work are courtesy of the NASA/SDO and HMI science teams, as well as the Geostationary Satellite System (GOES) team. This research has made use of NASA’s Astrophysics Data System (ADS). S.-H. Park was supported by the European Union Horizon 2020 research and innovation programme under grant agreement No. 640216 (FLARECAST; http://flarecast.eu ) and by MEXT/JSPS KAKENHI Grant No. JP15H05814.
Disclosure of Potential Conflicts of Interest
The authors declare that they have no conflicts of interest.
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