Evolution of the envelope structure during the first four years after the onset of the dynamical simulation. Panels (a) and (b) show models with envelope masses of 0.64 M_⊙ and 0.25 M_⊙, respectively. The solid black line indicates the stellar radius, while the dashed gray lines mark the radial positions that divide the envelope mass into 20 equal parts. The color bar represents the relative fraction of ionized hydrogen.