Damping time over period (quality factor) against magnetic field strength, for 3 heating models with differing dependencies on magnetic field strength, which are each coloured (Eqs. (23), (18)). Top: quality factors calculated for plasma parameters corresponding to an upwardly propagating slow wave in a coronal fan loop above a sunspot, T = 0.63 MK, electron density of n_e = 1.5 × 10⁹ cm⁻³, and periodicity set to 3.0 min corresponding to a wavelength of λ = 22 Mm. Middle: quality factors calculated for a slow wave propagating in a coronal plume, T = 1.3 MK, n_e = 5 × 10⁸ cm⁻³, and wavelength λ set to 100 Mm corresponding to a periodicity of 9 min. Bottom: quality factors calculated for a standing slow wave in a hot loop observed by SUMER, T = 6.3 MK, n_e = 1 × 10¹⁰ cm⁻³, λ = 250 Mm yielding a periodicity of 11 min. Grey shading marks the β > 1 region, and the dotted line in the bottom plot marks a region in which 𝒯_M < 0 and so the effect of thermal misbalance is destabilising the plasma.