Southern part of Mon OB 1 east (corresponding to the red box in Fig. 3) with the POS magnetic field orientation represented by the blue segments, overlaid on the TRAO ¹²CO integrated intensity gray-scale map. Top row: red segments show the orientation of the rotated intensity gradients based on the ¹²CO and ¹³CO tracers (panels a and b respectively). Bottom row: magenta segments show the orientation of the rotated velocity gradients based on the ¹²CO and ¹³CO tracers (c and d respectively).