Flux density, S_ν, for T = 7500 K, U = 40 km s⁻¹, L = 0.5 pc, ν = 300 MHz, and θ_b = 10″ in parameter space (n, B) for three different values of ionisation fraction as labelled on right-hand side of each subplot. Dark and light grey-shaded areas in each subplot show the region of the parameter space where the condition of super-Alfvénic flow and ion-neutral coupling is not satisfied, respectively. Solid black lines in each subplot show the iso-flux density at 1 and 10 mJy in logarithmic scale (from the bottom up).