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Can Solar 6 Li Really Be Explained by Galactic Cosmic Rays?

Can Solar 6 Li Really Be Explained by Galactic Cosmic Rays?. Tijana Prodanović University of Novi Sad, Serbia Brian D. Fields University of Illinois at Urbana-Champaign. July 5 th , 200 7 30 th ICRC, Merida, Mexico. Outline.

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Can Solar 6 Li Really Be Explained by Galactic Cosmic Rays?

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  1. Can Solar 6Li Really Be Explained by Galactic Cosmic Rays? Tijana Prodanović University of Novi Sad, Serbia Brian D. Fields University of Illinois at Urbana-Champaign July 5th, 2007 30th ICRC, Merida, Mexico

  2. Outline • Standard 6Li origin: Galactic Cosmic-Ray (GCR) nucleosynthesis • New observations indicate new 6Li source • CR interactions: Li & gamma-rays connected • Use extragalactic gamma-ray background (EGRB) to constrain GCR made 6Li • EGRB allows only ~50% of solar 6Li to be made by GCRs! • New source? MW higher CR flux? Low-energy CR component? 30th ICRC, Mexico

  3. How Well Do We Understand 6Li? • 7Li origin: cosmic rays + BBN • But 6Li only made by cosmic rays via fusion and spallation • Standard assumption: 6LiSolarmade by Galactic CRs • But new observations indicate a 6LiSolar plateau? New source of 6Li needed? Asplund et al.(2006) 30th ICRC, Mexico

  4. Lithium Cosmic-Ray Interactions • Hadronic cosmic-ray interaction production of • Pionic Gamma Rays 6Li & pionic gamma-rays connected! 30th ICRC, Mexico

  5. Li-g-ray Connection • Any cosmic-ray source produces both gamma-rays and lithium • Connected essentially with ratio of reaction rates (Fields and Prodanović 2005) • Li abundance: local CR fluence • Diffuse extragalactic : CR fluence across Universe • Use gamma rays to constrain Li! 30th ICRC, Mexico

  6. Galactic CRs and 6Li : Results Prodanović & Fields (2006) • Pionic gamma-ray fraction • Normalized to the Milky Way (blue) • ~30% of the total EGRB (normal gal.) • 6Li production channels included • fusion • spallation • 2-step reactions, eg. • Account for astration • Gamma rays allow for only ~50% of 6Li to be produced by GCRs! 30th ICRC, Mexico

  7. Implications & Conclusions • Only ~ 50% of solar 6Li can be explained by GCRs without overproducing gamma-rays • Need new important 6Li source • Recent observations in halo stars: 6Li plateau? But at 10% level of solar (Asplund et al. 2006) • Milky Way GCR flux higher than the cosmic mean? • Implications for star-formation rate • Low-energy CR component? • Energetics and LiBeB ratio constraints 30th ICRC, Mexico

  8. Thank You! 30th ICRC, Mexico

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