Energy Extraction via Magnetic Reconnection in Kerr-Sen-AdS$_{4}$ Black Hole: Circular Plasma and Plunging Plasma

Abstract: This paper investigates the power and efficiency of energy extraction via magnetic reconnection in the Kerr-Sen-AdS$_{4}$ black hole, focusing primarily on the circular orbit region and the plunging region. After introducing the black hole event horizon, boundary of the ergosphere, and photon sphere radius, we first study the energy extraction via magnetic reconnection in circular orbit region. We plot the allowed regions for energy extraction and present the energy extraction power and efficiency, comparing them with the Blandford-Znajek (BZ) mechanism. It was found that energy extraction is still possible even at a spin parameter of 0.5, which is lower than previous results, and the power can be higher than the BZ process in certain regions. In addition, we find the dilatonic scalar charge $b$ and the AdS radius $l$ contribute to lowering the spin threshold required for energy extraction. We also study the energy extraction in the plunging region by analyzing the allowed regions for energy extraction, and the power as well as efficiency. It was found that the energy extraction is possible even at a spin as low as 0.25. Especially, we find that parameter $b$ promotes lowering the energy extraction spin threshold while $l$ suppresses it, which is different from the circular orbit case. Moreover, the power and efficiency of energy extraction in the plunging region are higher than in the circular orbit region, indicating a stronger energy extraction capability in the plunging region.