Production and acceleration mechanisms of ultra-high-energy cosmic rays (UHECRs) of energy $>10^{20}$eV, clearly beyond the GZK-cutoff limit remain unclear that points to exotic nature of the phenomena. Recent observations of extragalactic neutrino may indicate the source of UHECRs being an extragalactic supermassive black hole (SMBH). We demonstrate that ultra-efficient energy extraction from rotating SMBH driven by the magnetic Penrose process (MPP) could indeed foot the bill. We envision ionization of neutral particles, such as neutron beta-decay, skirting close to the black hole horizon that energizes protons to over $10^{20}$eV for SMBH of mass $10^9 M_{\odot}$ and magnetic field of strength $10^4$G. Applied to Galactic center SMBH we have proton energy of order $\approx 10^{15.6}$eV that coincides with the knee of the cosmic ray spectra. We show that large $\gamma_z$ factors of high-energy particles along the escaping directions occur only in the presence of induced charge of the black hole that is known as the Wald charge in the case of uniform magnetic field. It is remarkable that the process neither requires extended acceleration zone, nor fine-tuning of accreting matter parameters. Further, this leads to certain verifiable constraints on SMBH's mass and magnetic field strength as UHECRs sources. This clearly makes ultra-efficient regime of MPP one of the most promising mechanisms for fueling UHECRs powerhouse.

中文翻译：

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超大质量黑洞可能是超高能宇宙射线的来源

能量 $>10^{20}$eV 的超高能宇宙射线 (UHECR) 的产生和加速机制显然超出了 GZK 截止极限，但仍不清楚，这表明该现象的奇异性质。最近对河外中微子的观察可能表明 UHECR 的来源是河外超大质量黑洞 (SMBH)。我们证明了由磁性彭罗斯过程 (MPP) 驱动的旋转 SMBH 的超高效能量提取确实可以支付费用。我们设想中性粒子的电离，例如中子β衰变，绕过黑洞视界，对于质量为 $10^9 M_{\odot}$ 的 SMBH 和磁场，质子将质子激发到超过 $10^{20}$eV强度 $10^4$G。应用于银河系中心 SMBH，我们具有 $\approx 10^{15.6}$eV 量级的质子能量，与宇宙射线光谱的拐点重合。我们表明，沿逃逸方向的高能粒子的大 $\gamma_z$ 因子仅在存在黑洞感应电荷的情况下发生，即均匀磁场情况下的 Wald 电荷。值得注意的是，该过程既不需要扩展加速区，也不需要对吸积物质参数进行微调。此外，这对作为 UHECR 来源的 SMBH 的质量和磁场强度产生了某些可验证的限制。这显然使超高效 MPP 制度成为推动 UHECR 发电站最有前途的机制之一。值得注意的是，该过程既不需要扩展加速区，也不需要对吸积物质参数进行微调。此外，这对作为 UHECR 来源的 SMBH 的质量和磁场强度产生了某些可验证的限制。这显然使超高效 MPP 制度成为推动 UHECR 发电站最有前途的机制之一。值得注意的是，该过程既不需要扩展加速区，也不需要对吸积物质参数进行微调。此外，这对作为 UHECR 来源的 SMBH 的质量和磁场强度产生了某些可验证的限制。这显然使超高效 MPP 制度成为推动 UHECR 发电站最有前途的机制之一。