  Slow magnetoacoustic waves observed in the solar corona are used as
seismological probes of plasma parameters. It has been shown that dispersion
properties of such waves can vary significantly under the influence of the
wave-induced thermal misbalance. In the current research, we study the effect
of misbalance on waves inside the magnetic-flux tube under the second-order
thin-flux-tube approximation. Using the parameters of active region fan coronal
loops, we calculated wave properties such as the phase speed and decrement. It
is shown that neglecting thermal misbalance may be the reason for the
substantial divergence between seismological and spectrometric estimations of
plasma parameters. We also show that the frequency dependence of phase speed is
affected by two features, namely the geometric dispersion and the dispersion
caused by the thermal misbalance. In contrast to the phase speed, the wave
decrement primarily is affected by the thermal misbalance only. The
dependencies of the phase speed and decrement of the slow wave on magnetic
field and tube cross-section are also analyzed.
