Revival of the Penrose Process for Astrophysical Applications

By utilizing the curious existence of negative energy orbits outside the event horizon of the Kerr black hole, Penrose proposed that rotational energy of the black hole can be extracted. It was independently shown by Bardeen et al. (1972) and Wald (1974) that this process cannot offer an astrophysically viable mechanism for high-energy jets, because for significant gain in energy the breakup of the incident particle must itself be relativistic. In this paper, it is shown that the inconvenient requirement of relativistic splitting could be easily overcome for a black hole immersed in an electromagnetic field.