  We study the average rate of change of energy for a static atom immersed in a
thermal bath of electromagnetic radiation in the cosmic string spacetime and
separately calculate the contributions of thermal fluctuations and radiation
reaction. We find that the transition rates are crucially dependent on the
atom-string distance and polarization of the atom and they in general oscillate
as the atom-string distance varies. Moreover, the atomic transition rates in
the cosmic string spacetime can be larger or smaller than those in Minkowski
spacetime contingent upon the atomic polarization and position. In particular,
when located on the string, ground-state atoms can make a transition to excited
states only if they are polarizable parallel to the string, whereas ground
state atoms polarizable only perpendicular to the string are stable as if they
were in a vacuum, even if they are immersed in a thermal bath. Our results
suggest that the influence of a cosmic string is very similar to that of a
reflecting boundary in Minkowski spacetime.
