  Understanding the stability of the magnetic field in radiation zones is of
crucial importance for various processes in stellar interior like mixing,
circulation and angular momentum transport. The stability properties of a star
containing a prominent toroidal field in a radiation zone is investigated by
means of a linear stability analysis in the Boussinesq approximation taking
into account the effect of thermal conductivity. The growth rate of the
instability is explicitly calculated and the effects of stable stratification
and heat transport are discussed in detail. It is argued that the stabilizing
influence of gravity can never entirely suppress the instability caused by
electric currents in radiation zones although the stable stratification can
significantly decrease the growth rate of instability
