Evolution of the tube wave amplitude with distance along the plume for different values of the magnetic field strength in the plume. The dashed, dotted, dash-dotted, dash-double-dotted, and dash-triple-dotted lines correspond to B₀ = 10,5.0,1.5,1.0, and 0.5 G, respectively. The Alfvén speed is 866, 433, 130, 87, and 43 km s^-1, respectively; the sound speed is 175 km s^-1. The solid line corresponds to plane sound waves (or the infinitely strong magnetic field). The effective viscosity is 2.4 × 10¹⁴ cm² s^-1, the wave period is 600 s.