Snapshots of the perturbations of the physical parameters in a plasma cylinder at t = 3 (the time is normalised to w/C_Ae): the mass density ϱ (top left panel), the longitudinal component of the magnetic field B_z (bottom left panel), the transverse component of the velocity V_y (top right panel), and the longitudinal component of the velocity V_z (bottom right panel). The spatial coordinates are measured in units of w that is the half width of the cylinder.