  The presence of magneto-acoustic waves in magnetic structures in the solar
atmosphere is well-documented. Applying the technique of solar
magneto-seismology (SMS) allows us to infer the background properties of these
structures. Here, we aim to identify properties of the observed
magneto-acoustic waves and study the background properties of magnetic
structures within the lower solar atmosphere. Using the Dutch Open Telescope
(DOT) and Rapid Oscillations in the Solar Atmosphere (ROSA) instruments, we
captured two series of high-resolution intensity images with short cadence of
two isolated magnetic pores. Combining wavelet analysis and empirical mode
decomposition (EMD), we determined characteristic periods within the
cross-sectional (i.e., area) and intensity time series. Then, by applying the
theory of linear magnetohydrodynamics (MHD), we identified the mode of these
oscillations within the MHD framework. Several oscillations have been detected
within these two magnetic pores. Their periods range from 3 to 20 minutes.
Combining wavelet analysis and EMD enables us to confidently find the phase
difference between the area and intensity oscillations. From these observed
features, we concluded that the detected oscillations can be classified as slow
sausage MHD waves. Further, we determined several key properties of these
oscillations such as the radial velocity perturbation, magnetic field
perturbation and vertical wavenumber using solar magnetoseismology. The
estimated range of the related wavenumbers reveals that these oscillations are
trapped within these magnetic structures. Our results suggest that the detected
oscillations are standing harmonics, and, this allows us to estimate the
expansion factor of the waveguides by employing SMS. The calculated expansion
factor ranges from 4-12.
