Mean galactic magnetic field from our model as a function of the stream cold mass flux entering the halo Ṁ_s,0. The cold mass flux is obtained by varying its number density n_s ∈ [0.001,0.1] cm⁻³ for different stream radii R_s = (0.3, 3, 30) kpc (plain, dashed and dotted lines) and for different Mach number ℳ = 0.5, 1, 2 (light to dark colours). The red and blue colour maps show results for the default case B_s and the no-stretching case (see Sect. 3.3), respectively. The vertical grey line shows the maximum cold mass flux simulated in the simulations suite.