Observations of Extremely Strong Magnetic Fields in Active Region NOAA 12673 Using GST Magnetic Field Measurement

Abstract We present a detailed study of very strong magnetic fields in the NOAA Active Region (AR) 12673, which was most flare productive AR solar cycle 24. It produced four X-class flares including X9.3 on 2017 September 6 and X8.2 limb event 10. Our analysis is based direct measurements full Zeeman splitting Fe i 1564.85 nm line using all Stokes I, Q, U, V profiles. This approach allowed us to obtain reliable estimates magnitude independent filling factor atmosphere models. Thus, strongest up 5.5 kG were found light bridge (LB) spot, while dark umbra did not exceed 4 kG. In case LB, field related underlying continuum intensity, umbral we observed well-known anticorrelation between intensity magnitude. this study, LB cospatial with polarity inversion δ -sunspot, speculate that horizontal may be associated compact twisted flux rope at or near photosphere. A comparison depth π σ components showed are, average, more than those umbra.