We investigate the impact of spatial variations in the ionized fraction during reionization on temperature anisotropies in the CMB .
We combine simulations of large scale structure to describe the underlying density field with an analytic model based on extended Press-Schechter theory to track the reionization process .
We find that the power spectrum of the induced CMB anisotropies depends sensitively on the character of the reionization epoch .
Models that differ in the extent of the “ patchy phase ” could be distinguished by future experiments such as the Atacama Cosmology Telescope ( ACT ) and the South Pole Telescope ( SPT ) .
In our models , the patchy signal peaks at l \simeq 2000 , where it can be four times larger than the kinetic Sunyaev-Zel ’ dovich ( kSZ ) /Ostriker-Vishniac ( OV ) signal ( \Delta T _ { tot } \simeq 2.6 \mu K ) .
On scales beyond l \simeq 4000 the total Doppler signal is dominated by kSZ/OV , but the patchy signal can contribute up to 30 % to the power spectrum .
The effect of patchy reionization is largest on scales where the primordial CMB anisotropies dominate .
Ignoring this contribution could lead to significant biases in the determination of cosmological parameters derived from CMB temperature measurements .
Improvements in the theoretical modeling of the reionization epoch will become increasingly important to interpret the results of upcoming experiments .