Abstract
Magnetic Penrose process (MPP) is not only the most exciting and fascinating process mining the rotational energy of black hole but it is also the favored astrophysically viable mechanism for high energy sources and phenomena. It operates in three regimes of efficiency, namely low, moderate and ultra, depending on the magnetization and charging of spinning black holes in astrophysical setting. In this paper, we revisit MPP with a comprehensive discussion of its physics in different regimes, and compare its operation with other competing mechanisms. We show that MPP could in principle foot the bill for powering engine of such phenomena as ultra-high-energy cosmic rays, relativistic jets, fast radio bursts, quasars, AGNs, etc. Further, it also leads to a number of important observable predictions. All this beautifully bears out the promise of a new vista of energy powerhouse heralded by Roger Penrose half a century ago through this process, and it has today risen in its magnetically empowered version of mid 1980s from a purely thought experiment of academic interest to a realistic powering mechanism for various high-energy astrophysical phenomena.
Highlights
Among the experimental tests successfully passed by Einstein’s general theory of relativity are the tests of precession of Mercury’s perihelion, deflection of photons by Sun’s gravity, measurement of gravitational redshift, orbital decay of binary pulsars [1], direct detection of gravitational waves [2], investigation of properties of the Galactic center supermassive black hole [3], and others
We show that the cosmic rays with the highest detected energy in the range 1018 –1020 eV can be explained by neutron beta-decay in ergosphere of supermassive black hole (SMBH) of mass 109 M and magnetic field 104 G
Axial symmetry of spacetime and electromagnetic field is what is required for Magnetic Penrose process (MPP) to operate in three regimes of efficiency depending upon the two parameters, magnetic field strength and charge to mass ratio of particles involved in the process of energy extraction
Summary
Among the experimental tests successfully passed by Einstein’s general theory of relativity are the tests of precession of Mercury’s perihelion, deflection of photons by Sun’s gravity, measurement of gravitational redshift, orbital decay of binary pulsars [1], direct detection of gravitational waves [2], investigation of properties of the Galactic center supermassive black hole [3], and others. In ergosphere where gtt > 0, there exist particle orbits of negative energy states relative to infinity This is the key property that drives Penrose process of energy extraction from a rotating black hole. As in the case of MPP, black hole’s rotation generates electric currents along the horizon surface which convert mechanical spin energy of a black hole into electromagnetic energy to be extracted Both BZ and MPP act due to existence of quadrupole electric field, being produced by twisting of magnetic field lines. It was agreed that CPP was unlikely to be relevant in realistic high-energy phenomena, since the efficiency of the process in astrophysical situations (i.e., non-extremal black hole, collision occurring not exactly on horizon, incident particle falls from infinity) was severely constrained with maximum ηCPP < 15 [33].
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