  Primordial tangled cosmological Magnetic Fields source rotational velocity
perturbations of the baryon fluid, even in the post-recombination universe.
These vortical modes inturn leave a characteristic imprint on the temperature
anisotropy of the Cosmic Microwave Background (CMB), if the CMB photons can be
re-scatterred after recombination. Observations from WMAP indicate that the
Universe underwent a relatively early re-ionization ($z_{ri} \sim 15$), which
does indeed lead to a significant optical depth for re-scattering of CMB
photons after the re-ionization epoch. We compute the resulting additional
temperature anisotropies, induced by primordial magnetic fields in the
post-recombination universe. We show that in models with early re-ionization, a
nearly scale-invariant spectrum of tangled magnetic fields which redshift to a
present value of $B_0 \sim 3 \times 10^{-9}$ Gauss, produce vector mode
perturbations which in turn induce additional temperature anisotropy of about
0.3 to 0.4 $ \mu$K over very small angular scales, with $ l$ upto $\sim 10000 $
or so.
