Galactic Modulation of Extragalactic Cosmic Rays: -- A Possible Origin of the Knee in the Cosmic Ray Spectrumc --

The existence of the spectral break around $\sim 3 \times 10^{15}$ eV in thecosmic ray spectrum (referred to as the `knee') is one of the biggest questionsin cosmic ray astrophysics. At the same time, the origin of cosmic rays abovethe knee energies (between 10$^{15}$ and 10$^{18}$ eV) is also still unsettled.In this paper, we investigate how the hypothetical extragalactic CRs aftermodulated by the galactic wind contribute to the knee in the CR spectrum. Wenumerically calculate the modulated energy spectrum of the hypothetical cosmicrays coming into the galaxy from just outside of the ``galactic sphere'' wherethe galactic wind terminates. We show that the observed knee structure isreproduced well by a superposition of the modulated component and the galacticcosmic rays originating in supernova remnants.Comment: Accepted for publication in Progress of Theoretical Physic