The effect of a forced dilution air jet, introduced through the combustor shell, on the air/ fuel mixing in the combustion chamber has been investigated. Thermocouple- based temperature measurements have been made at a number of forcing frequencies in the range 100 - 1100 Hz and blowing ratios in the range 10 - 15. Open- loop integral flame response to forcing has also been acquired by recording pressure and heat release spectra. A CH- radical imaging technique is used to provide spatially and temporally resolved information about the heat release behavior. The results exhibit that the mean temperature field inside the main reaction zone can be significantly altered as a consequence of air- jet modulation. The most significant effects are observed by forcing at vertical locations that are close to the dump plane. Enhancements in temperature of the order of 100 - 200 degrees C and reduction in pattern factor of the order of 40% were observed, with the lowest pattern factors achieved at the lowest forcing frequency of 100 Hz.