# Accelerated protons produced by magnetic Penrose process in Sgr A*

**Authors:** Myeonghwan Oh, Myeong-Gu Park  
**arXiv:** [2406.04764](https://arxiv.org/abs/2406.04764)  
**Date:** 2024-06-07  
**Summary page:** https://www.summarizepaper.com/en/paper/2406.04764v1/

## Key points

- Study by Myeonghwan Oh and Myeong-Gu Park in Physical Review D focuses on Magnetic Penrose Process (MPP) for energy extraction from rotating black holes
- MPP offers more accessible route to producing ultra-high energy cosmic rays compared to traditional Penrose process
- Efficiency of proton production through MPP maximized by considering decay of neutrons near rotating black hole, particularly investigating supermassive black hole in Sagittarius A* (Sgr A*)
- Neutrons generated through nuclear reactions in Sgr A* can be accelerated to high energies through MPP
- Team calculates rate of proton acceleration from Sgr A*, estimating gamma-ray flux produced by these accelerated protons reaching Earth and the flux of accelerated protons themselves during journey
- Very high-energy gamma rays exceeding 10 TeV constitute significant portion of observed gamma-ray fluxes from sources like HESS J1745-290 and regions around 100 TeV
- Accelerated proton flux amounts to approximately 1.6-4.1% of cosmic ray proton flux detected by experiments like KASCADE at around 1 PeV when considering parameters such as dimensionless spin parameter of 0.5 and magnetic field strength near black hole of 100 G
- Acceleration model most effective around black holes with masses not significantly greater than approximately 10^8 solar masses due to constraints related to neutron decay times and transportation from accretion flows to acceleration zones
- Study highlights how processes like MPP near supermassive black holes contribute significantly to understanding high-energy cosmic phenomena and their impact on astrophysical environments

## Summary

A recent study by Myeonghwan Oh and Myeong-Gu Park, published in Physical Review D, focuses on the Magnetic Penrose Process (MPP) as a mechanism for extracting energy from rotating black holes. Unlike the traditional Penrose process, which is rarely met in common astrophysical scenarios, the MPP offers a more accessible route to producing ultra-high energy cosmic rays. The efficiency of proton production through the MPP is maximized by considering the decay of neutrons near a rotating black hole. Specifically investigating the supermassive black hole located in Sagittarius A* (Sgr A*), known for its radiatively inefficient accretion flow capable of generating neutrons through nuclear reactions. These neutrons can then be accelerated to high energies through the MPP. The team calculates the rate at which protons are accelerated from Sgr A*, estimating both the gamma-ray flux produced by these accelerated protons reaching Earth and the flux of accelerated protons themselves during this journey. Their findings reveal that very high-energy gamma rays with energies exceeding 10 TeV constitute a significant portion of observed gamma-ray fluxes from sources like HESS J1745-290 and regions around 100 TeV. Additionally, when considering parameters such as a dimensionless spin parameter of 0.5 and a magnetic field strength near the black hole of 100 G, the accelerated proton flux amounts to approximately 1.6-4.1% of cosmic ray proton flux detected by experiments like KASCADE at around 1 PeV. It is important to note that this acceleration model is most effective around black holes with masses not significantly greater than approximately 10^8 solar masses due to constraints related to neutron decay times and transportation from accretion flows to acceleration zones. This study sheds light on how processes like the MPP near supermassive black holes can contribute significantly to our understanding of high-energy cosmic phenomena and their impact on astrophysical environments.