Solar Flare Particle Effects and Seasonal Radiocarbon Variations in Tree Rings of the Northern and Southern Hemispheres

Measurements of ∆14C and δ13C, separately in early wood and late wood of two Mediterranean pine species, with a nearly year-long growth season, were made to better define possible solar flare particle effects. The measurements were made for suitable periods around the years of big flares (e.g., 1942, 1946, 1989) in Pinus pinea of the Adriatic area and Pinus halepensis from South Australia. We found that the 14C concentration is consistently greater in early wood than in late wood of the same growth ring and considerably higher in the Australian samples than in the European samples. The data so far reveal no evidence of solar-flare effect.