Current helicity spatial distribution and chunk evolution for AR 12673. (a) Radial magnetic field at three time points (column titles). (b) Current helicity distribution at the same time points; green lines mark PILs. (c) Chunk masks (spatially coherent regions with consistent helicity sign) at the same time points; color intensity represents pixel count in each chunk; only chunks with dominant negative helicity are shown. (d) Chunk pixel count versus total helicity scatter plots with 2D histogram backgrounds. (e) MEAN term (red) and -VAR term (blue) evolution. Green dashed lines indicate column header times; black lines mark M-class and above flare peaks.