COSMIC-RAY HELIUM HARDENING

被引：83

作者：

Ohira, Yutaka ^{[1
]}

Ioka, Kunihito ^{[1
]}

机构：

[1] KEK High Energy Accelerator Res Org, Inst Particle & Nucl Studies, Ctr Theory, Tsukuba, Ibaraki 3050801, Japan

来源：

ASTROPHYSICAL JOURNAL LETTERS | 2011年 / 729卷 / 01期

关键词：

acceleration of particles; cosmic rays; ISM: supernova remnants; shock waves; DIFFUSIVE SHOCK ACCELERATION; SUPERNOVA REMNANT SHOCKS; PARTICLE-ACCELERATION; STREAMING INSTABILITY; MAGNETIC-FIELD; DRIVEN INSTABILITY; WAVE DISSIPATION; MASSIVE STARS; SUPERBUBBLES; SPECTRUM;

D O I：

10.1088/2041-8205/729/1/L13

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

Recent observations by the CREAM and ATIC-2 experiments suggest that (1) the spectrum of cosmic-ray (CR) helium is harder than that of CR protons below the knee energy, 10(15)eV, and (2) all CR spectra become hard at greater than or similar to 10(11)eV nucleon(-1). We propose a new idea, that higher energy CRs are generated in a more helium-rich region, to explain the hardening without introducing different sources for CR helium. The helium-to-proton ratio at similar to 100 TeV exceeds the Big Bang abundance Y = 0.25 by several times, and the different spectrum is not reproduced within the diffusive shock acceleration theory. We argue that CRs are produced in a chemically enriched region, such as a superbubble, and the outward-decreasing abundance naturally leads to the hard spectrum of CR helium if CRs escape from the supernova remnant shock in an energy-dependent way. We provide a simple analytical spectrum that also fits well the hardening due to the decreasing Mach number in the hot superbubble with similar to 10(6) K. Our model predicts hard and concave spectra for heavier CR elements.

引用

页数：5

共 42 条

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