Extracting energy via magnetic reconnection from Kerr-de Sitter black holes

Abstract

It has been recently shown that magnetic reconnection can provide us a novel mechanism to extract black hole rotational energy from a Kerr black holes. In some certain values of parameters, such mechanism is found to be more efficient than the Blandford-Znajek mechanism. In this paper, we study the energy extraction from the Kerr-de Sitter black hole via this magnetic reconnection process. With the increase of the cosmological constant, a slowly spinning Kerr-de Sitter black hole can implement the energy extraction than its Kerr counterpart. Of particular interest is that although the numerical calculation shows that the maximum values of the power and efficiency decrease with the cosmological constant, Kerr-de Sitter black hole still has advantages when the black hole spin $a/M>1$ and the dominant reconnection $X$-point is far away from the event horizon. These results uncover the significant effects of cosmological constant on the energy extraction via the magnetic reconnection process.Comment: 16 pages, 11 figure