  Bulk motions of electrons along the line of sight induce secondary
temperature fluctuations in the post-decoupling, reionized universe. In the
presence of a magnetic field not only the scalar mode but also the vector mode
act as a source for the bulk motion. The resulting angular power spectrum of
temperature anisotropies of the cosmic microwave background is calculated
assuming a simple model of reionization.Contributions from the standard
adiabatic, curvature mode and a non helical magnetic field are included. The
contribution due to magnetic fields with field strengths of order nG and
negative magnetic spectral indices becomes important for multipoles larger than
$\ell \sim 10^4$.
