Philipp Mertsch
(Stanford University)

The CR anisotropy problem and the rise in the positron fraction

Recently, the AMS-02 collaboration has presented data on cosmic ray protons, Helium, electrons and positrons as well as the boron-to-carbon ratio. We present the first consistent modeling of these data, paying particular attention to the contribution due to production and acceleration of secondary electrons and positrons in nearby supernova remnants. This process results in an additional, harder component that becomes dominant at high energies and can explain the rise in the positron fraction observed earlier by PAMELA.

The observation of an anisotropy in the arrival direction of cosmic rays has been widely advertised as a means of finding such nearby sources. While no strong anisotropy has been observed yet, in the standard picture of cosmic ray transport the low level of the dipole amplitude is worrisome. I will show that taking into account the possible misalignment between the magnetic field and the direction of sources as well as stochastic effects for the turbulent field can significantly alleviate this problem, thus solving a long-standing problem.

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