Kerr black hole energy extraction, irreducible mass feedback, and the effect of captured particles charge

J. A. Rueda; R. Ruffini

doi:10.1140/epjc/s10052-024-13459-1

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2024) 84: 1166
https://doi.org/10.1140/epjc/s10052-024-13459-1

Regular Article

Kerr black hole energy extraction, irreducible mass feedback, and the effect of captured particles charge

J. A. Rueda¹^,2^,3^,4^,5^a and R. Ruffini¹^,2^,6

¹ ICRANet, Piazza della Repubblica 10, 65122, Pescara, Italy
² ICRA, Dipartimento di Fisica, Sapienza Università di Roma, P.le Aldo Moro 5, 00185, Rome, Italy
³ ICRANet-Ferrara, Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Saragat 1, 44122, Ferrara, Italy
⁴ Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Saragat 1, 44122, Ferrara, Italy
⁵ INAF, Istituto de Astrofisica e Planetologia Spaziali, Via Fosso del Cavaliere 100, 00133, Rome, Italy
⁶ INAF, Viale del Parco Mellini 84, 00136, Rome, Italy

^a jorge.rueda@icra.it

Received: 17 June 2024
Accepted: 6 October 2024
Published online: 18 November 2024

Abstract

We analyze the extraction of the rotational energy of a Kerr black hole (BH) endowed with a test charge and surrounded by an external test magnetic field and ionized low-density matter. For a magnetic field parallel to the BH spin, electrons move outward(inward) and protons inward(outward) in a region around the BH poles(equator). For zero charge, the polar region comprises spherical polar angles $- 60^{\circ} ≲ θ ≲ 60^{\circ}$ $-60^\circ \lesssim \theta \lesssim 60^\circ$ and the equatorial region $60^{\circ} ≲ θ ≲ 120^{\circ}$ $60^\circ \lesssim \theta \lesssim 120^\circ$ . The polar region shrinks for positive charge, and the equatorial region enlarges. For an isotropic particle density, we argue the BH could experience a cyclic behavior: starting from a zero charge, it accretes more polar protons than equatorial electrons, gaining net positive charge, energy and angular momentum. Then, the shrinking(enlarging) of the polar(equatorial) region makes it accrete more equatorial electrons than polar protons, gaining net negative charge, energy, and angular momentum. In this phase, the BH rotational energy is extracted. The extraction process continues until the new enlargement of the polar region reverses the situation, and the cycle repeats. We show that this electrodynamical process produces a relatively limited increase of the BH irreducible mass compared to gravitational mechanisms like the Penrose process, hence being a more efficient and promising mechanism for extracting the BH rotational energy.

© The Author(s) 2024

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