  This paper is concerned with a Cauchy problem for the three-dimensional (3D)
nonhomogeneous incompressible heat conducting magnetohydrodynamic (MHD)
equations in the whole space. First of all, we establish a weak Serrin-type
blowup criterion for the strong solutions. It is shown that for the Cauchy
problem of the 3D nonhomogeneous heat conducting MHD equations, the strong
solution exists globally if the velocity satisfies the weak Serrin's condition.
In particular, this criterion is independent of the absolute temperature and
magnetic field. Then as an immediate application, we prove the global existence
and uniqueness of strong solution to the 3D nonhomogeneous heat conducting MHD
equations under some smallness condition on the initial data. In addition, the
initial vacuum is allowed.
