Multiscale view of the B field toward the massive star-forming region G31.41+0.31. Panel (a): B-field segments (yellow) observed with the JCMT POL-2 (this work) with a primary beam FWHM of 12.6″ (Mairs et al. 2021) plotted in steps of 1 pixel with a scale of 12″ overlaid on the Spitzer GLIMPSE 8 μm image and IRAM-30m N₂H⁺ integrated-intensity map (cyan contours) from Beltrán et al. (2022b). Panel (b): B-field segments (yellow) observed with SMA plotted with a step of 1 pixel and JCMT POL-2 (red) overlaid on the Stokes I (blue and cyan contours) at 879 μm observed with the SMA and a synthesized beam of $1\stackrel{″}{.}34\times 0\stackrel{″}{.}83$ by Girart et al. (2009). Panel (c): B-field segments (yellow) plotted with a pixel step of 7 pixels overlaid on the Stokes I blue contours) at 1.3 mm observed with ALMA and a synthesized beam of $0\stackrel{″}{.}28\times 0\stackrel{″}{.}20$ by Beltrán et al. (2009). Panel (d): B-field segments (yellow) plotted with a pixel step of 7 pixels overlaid on the Stokes I (blue contours) at 3.1 mm with ALMA and a synthesized beam of $0\stackrel{″}{.}072\times 0\stackrel{″}{.}068$ (Beltrán et al. 2024). The (synthesized) beam of the different instruments is shown in the bottom left corner of each panel. Panel (e): B-field segments at different wavelengths and resolutions (see legend) overlaid on the 3.1 mm Stokes I intensity map (gray scale), same as panel (d). The blue cross indicates the center of intensity position. In panels b to d, A–D represent the four continuum protostars embedded in the HMC, and NE represents the continuum core, which is located northeast of the HMC (Beltrán et al. 2021).