Upper panels: behavior of the local thermal timescale in a model which fits f₁ as the radial fundamental (black line) and a model which fits f₁ as the first radial overtone (grey line). The horizontal lines mark the periods of selected modes (0.203 d in the left panel and 0.102 d in the right panel). Lower panels: differential work integral for the corresponding modes in the envelopes of both models (positive in driving zones, negative in damping zones).