Influence of the 11-yr solar cycle on the radiocarbon variations in the atmosphere

Variations in the radiocarbon concentration caused by secular changes in the solar activity are discussed. The radiocarbon data obtained by analysing annual tree ring samples taken for solar cycles 17 and 18 are presented. A comparison of radiocarbon data with sunspot numbers showed an anticorrelation dependence with phase shift of 3 years, i.e., the radiocarbon maximum lags behind the solar minimum by 3 years, and vice versa. A regression approximation to the observed data indicates a 0.7% amplitude oscillation over the 11-year solar cycle. The possible influence of solar flare particles on the observed radiocarbon variations is discussed. (author)