Upturn in the ratio of nuclei of Z=16–24 to iron observed in the ATIC experiment and the Local Bubble

The ratios of heavy nuclei from Sulfur (Z=16) to Chromium (Z=24) fluxes to the flux of iron nuclei were measured recently in the ATIC-2 experiment. These ratios were the decreasing functions of energy from 5 GeV/n to approximately 50 GeV/n as expected. However, an unexpected sharp upturn in the ratios was observed at energy ∼ 50 GeV/n. In this paper, we revise the data and show that the statistical confidence of the observed upturn in the ATIC data is 99.7% and some additional arguments supporting the phenomenon are presented. A possible cause of the upturn is discussed and it is demonstrated that it can be partially understood within a model of ‘Closed Galaxy with Bubbles’ (CGB). Some features and problems of the CGB model are discussed.