Left: spatiotemporal evolution of the fundamental harmonic of the slow mode (red circles), entropy mode (blue squares), and full numerical solution of Equations (1)–(4) (gray dashed) for loop temperature perturbation. The time dependence of the slow and entropy modes is given by Equations (13) and (14); the spatial structure of their amplitudes A_T,slow(z) and A_T,entropy(z) is obtained as described in Section 3.3. Right: same as left column but for plasma density perturbations.