2024/01/23 by Okamoto, Isao, Uchida, Toshio, Song, Yoogeun
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · doi:10.48550/arxiv.2401.12684
It is argued that the zero-angular-momentum-observers (ZAMOs) circulating with the frame-dragging-angular-velocity ω plays a leading part in energy extraction. When the condition Ω\rm F<Ω\rm H is satisfied, where Ω\rm H and Ω\rm F are the horizon and field-line (FL) angular-velocities (AVs), they will see that the null surface S\rm N with ω\rm N=Ω\rm F always exists in the force-free magnetosphere. The pivotal ZAMO-measured FLAV Ω\rm ZF ≡ Ω\rm F - ω changes sign on this surface S\rm N where the force-free and freezing-in conditions break down. The force-free magnetosphere is divided on this surface, with particle-current sources on it. The outer domain D\rm (out) outside S\rm N spins forward (Ω\rm ZF>0), whereas the inner domain D\rm (in) inside spins backward (Ω\rm ZF<0). Because the electric field \bf E\rm p reverses direction there, the Poynting flux reverses direction as well from outward to inward, though the positive angular momentum always flows outwardly. Electromagnetic self-extraction of energy will be possible only through the frame-dragged magnetosphere, with the inner domain D\rm (in) nested between the horizon and the surface S\rm N, when Ω\rm F<Ω\rm H is ensured by the 1st and 2nd laws of thermodynamics.