The impact of 11-year solar cycle variations on stratospheric ozone (O3) is studied with the Freie Universit¿t Berlin Climate Middle Atmosphere Model with interactive chemistry (FUB-CMAM-CHEM). To consider the effect of variations in charged particle precipitation we included an idealized NOx source in the upper mesosphere representing relativistic electron precipitation (REP). Our results suggest that the NOx source by particles and its transport from the mesosphere to the stratosphere in the polar vortex are important for the solar signal in stratospheric O3. We find a positive dipole O3 signal in the annual mean, peaking at 40--45 km at high latitudes and a negative O3 signal in the tropical lower stratosphere. This is similar to observations, but enhanced due to the idealized NOx source and at a lower altitude compared to the observed minimum. Our results imply that this negative O3 signal arises partly via chemical effects.