Effect of induced frame dragging on energy extraction from axially symmetric magnetized Reissner-Nordström BH and observational benchmarks

Abstract

In this paper, we probe the effect of induced frame dragging on the energy extraction process via magnetic reconnection in axially symmetric magnetized Reissner-Nordström black hole (MRNBH) spacetime and show the influence of BH charge $Q$ and the magnetic field $B$ parameters, respectively. We start by analyzing the metric and present the distinction between the geometrical and induced ergospheres. We argue that the induced ergosphere, unlike the geometric ergosphere, is not a property of the spacetime metric but rather a particle-dependent negative energy region that changes as the charge on the particle varies. We find the region where magnetic reconnection can extract energy from the axially symmetric MRNBH and determine the conditions required for this process. We further examine the energies of the accelerated and decelerated plasma outflows and the corresponding magnetic reconnection efficiency. We show that within the parameter ranges considered, the extraction efficiency increases with the MRNBH charge $Q$ and the magnetic field parameter $B$. For sufficiently large $B$, it reaches the efficiency comparable to that of an extremal Kerr BH case. Our results therefore show that electromagnetically induced frame dragging can support energy extraction efficiencies similar to those associated with rotation parameter. To connect with observations, we evaluate the reconnection power directly from the decelerated-plasma energy at infinity and compare it with the observed power scales of M87* and Sgr~A*. For $Q=M$, reconnection extraction appears in our scan only for $|B|M\gtrsim0.2$ ($B\sim10^{9}\,\mathrm{G}$ for M87*, $\sim10^{12}\,\mathrm{G}$ for Sgr~A*), where $P_{\mathrm{ext}}\sim10^{53}$--$10^{57}\,\mathrm{erg\,s^{-1}}$ exceeds the observed power scales by many orders of magnitude.