Characteristics of Magnetoacoustic Waves and Coronal Seismology

We model fast magnetohydrodynamic sausage and kink wave characteristics propagating in solar slab-like plasma structures. By implementing Cartesian coordinates, explicit expressions are provided governing the dependence of the frequency, damping, damping time, phase, and group speeds of fast sausage and kink waves on the wavenumber and density contrasts of solar slab-like plasmas. Explicit expressions are presented through equilibrium conditions and physical parameters controlling the plasma structure. Solutions of the explicit expressions are compared with numerical results. The overlap of curves proves adequate for the robustness of the explicit expressions. Kink modes possess higher frequencies compared to sausage modes in the leaky regime, while the sausage mode phase speed increases more rapidly compared to the kink speed. This explains the higher group speeds of sausage waves compared to kink waves around the cutoff. Sausage waves damp quicker compared with kink waves. The damping is inversely proportional to the mode number. As the damping time is directly proportional with the wavenumber, the damping time is much higher around the cutoff frequency compared to the long wavelength limit. The presented expressions prove adequate for coronal seismology, where, as the magnetoacoustic oscillations damp and disappear, the local and neighboring physical parameters and conditions could be estimated. As leaky kink modes live longer than sausage modes, they have a higher chance of being observed while transporting energy to a broader region. Sausage modes penetrate less due to fast damping providing higher heating rates in shorter ranges. Both modes contribute to coronal heating in various scales.