He I D3 and 10830 observations of the flare-productive active region AR 12673 on 2017 September 7

The active region NOAA AR 12673 is the most flare productive active region in the solar cycle 24. On 2017 September 07, it produced an X1.3 flare, three M-class, and several C-class flares. We successfully observed several C-class flares from 16:50 UT to 22:00 UT using the 1.6m Goode Solar Telescope (GST; formerly NST) at Big Bear Solar Observatory (BBSO). The GST provides us with unprecedented high-resolution data of the Sun since 2009. Interestingly, we observed the active region in He I D3 and 10830 lines simultaneously. The data shows several interesting features: (1) D3 emission seems to be much weaker than 10830 emission around 21:29 UT; (2) a small loop seen in 10830 is moving upward and is brightened around 21:16 UT, but it is not clear in D3; (3) there are waves in the penumbra seen in 10830 line center; (4) there is a jet with twisting motion. In this presentation, we will give the results of our analysis and interpretations.