Horizontally averaged radial velocity v_r plotted as modified radial coordinate x (≡ r − R₀/r) vs. time. The leftmost column represents the non-magnetic case for a direct comparison. The top row shows models with a radial magnetic field of 1, 10, and 20 kG. Similarly, the bottom panels show models with a horizontal magnetic field of 1, 10, and 20 kG. The dotted black line represents the photospheric radius (R_phot ≡ r(τ = 2/3) and the solid black line denotes the location of the iron opacity peak (T ~ 1.6 × 10⁵ K). The radial magnetic field does not inhibit up-and-down piston-like motions of the gas, whereas the strong horizontal magnetic field can fully suppress it. This figure also demonstrates clearly how velocity dispersion is initiated near the iron opacity peak (solid black line). We show only the final ~3 d of simulation for all models. Coincidentally, the model with 1 kG radial magnetic field was caught in one of the episodes of outbursts, which is also visible in Fig. 3, albeit less prominently.