Outline of a magnetic field and cloud geometry consistent with the HAWC+ observations. Blue and magenta vertical arrows indicate the global structure of the magnetic field. The blue cylinder represents a dense cloud, such as the DR21 Main Ridge. The green layers represent a sheet that envelopes the dense cloud and is oriented perpendicular to the magnetic field. Panel (a) presents a view in which the observer is located toward the left of the figure; the line of sight in this model is nearly perpendicular to ﹩{\boldsymbol{B}}﹩. Gray cloudlets represent gas parcels following trajectories parallel to ﹩{\boldsymbol{B}}﹩ that accrete onto the sheet or the dense cloud, depending on the impact parameter of the field line they follow. Acceleration vectors span nonzero angles with the local field line for nonzero impact parameters. Panel (b) provides a rotated view closely aligned with the observer’s perspective.