Asymmeteries in the gas surface density close to the planet as a cause for the torque oscillations observed in Fig. 5. Left panel: torque evolution as a function of time for the low X-ray luminosity case. The blue line corresponds to the “raw” torque directly obtained from FARGO, while the orange line shows the smoothed torque using the previously described Savitzky-Golay filter. The black line corresponds to the azimuthally averaged surface density profile at the planet location. The torques were normalised by the normalisation factor Γ₀ (cf. Eq. (10)). Right panel: corresponding 2D surface density distribution for the high and low torque peaks with respectto the reference step.