Spitzer images of SDC18 at 24 μm (red), 8 μm (green), and 5.8 μm (blue), together with JCMT/POL-2 850μm dust continuum contours (left panel) and magnetic field structures (right panel). The contours denote the 50, 500, and 1000 mJy beam⁻¹ of the JCMT total intensity. Orange contours are the boundaries of SDC18-N and SDC18-S at filament-embedded clump scale determined by the dendrogram analysis. The JCMT/POL-2 magnetic field orientations with P> 3σ_P are in yellow and in red for 3σ_P > P > 2σ_P. White segments are the larger-scale Planck magnetic field orientations inferred from 90° rotation of polarization at 353 GHz (∼ 5ʹ) in a pixel size of 103ʺ.