Top: space–time distribution of the midplane temperature. The location of the snowline (T_mid = 170 K) is denoted by the thicker solid line. Bottom: space–time distribution of the fourth power of the temperature ratio (T_acc/T_irr)⁴ between accretion heating and irradiation heating, indicating the contribution of accretion heating to the disk temperature. The dotted white line shows the boundary of the accretion-heated region (i.e., (T_acc/T_irr)⁴ = 1) in Fid for reference.