  We study the influence of constant magnetic field combined with a field
induced by the external thermal environment on the atomic decay rates. The
importance of radiative corrections, including magnetic interaction, is
demonstrated for hydrogen and hydrogen-like ions with low nuclear charge values
$Z$. Based on the quantum electrodynamics description, the principal
possibility of determining the $g$-factor by observing fluorescence is shown.
The considered effects can be used in precision spectroscopic experiments and
astrophysical studies.
