Net flux (F_I, upper) and circularly polarized fraction (F_V, lower) simulated for the reference circumstellar disk model (113.144 GHz CN line emission). In the lower images, the derivative of F_I is shown and fitted to F_V to estimate the LOS magnetic field strength (red dashed line). The profiles on the left, middle, and right side are simulated with an abundance of CN / H =10^-7, CN / H =4 × 10^-9, and CN / H =10^-9, respectively.