Blandford–Znajek process

Summary

The Blandford–Znajek process extracts rotational energy from a spinning black hole through magnetic field lines that thread its event horizon. Surrounding matter keeps the field lines in place, and the black hole drags them into rotation. So they carry a Poynting flux of electromagnetic energy outward. The process is a leading explanation for the powerful relativistic jets of active galactic nuclei and gamma-ray bursts. Its power grows with the square of the magnetic flux through the horizon and, for moderate spins, with the square of the spin.