Which process can power black hole jets by extracting rotational energy through magnetic fields?

The Blandford–Znajek process can power black-hole jets by extracting rotational energy through magnetic fields.

Proposed by Roger Blandford and Roman Znajek in 1977, the mechanism applies to a spinning Kerr black hole surrounded by an accretion disk and a strong, organized magnetic field. Magnetic field lines threading the black hole’s magnetosphere interact with the rotating spacetime around it, allowing energy and angular momentum to flow outward as electromagnetic power.

The ergosphere is central to the process. This region outside the event horizon is dragged around by the black hole’s rotation, and currents in the magnetosphere can tap the hole’s spin energy. The extracted power can help launch narrow, relativistic jets that extend far beyond the surrounding accretion disk, especially in active galactic nuclei and quasars.

The Blandford–Znajek process is not the same as the Penrose process, although both draw on rotational energy and involve the ergosphere. The Urca process concerns neutrino cooling in dense matter, while the CNO cycle is a stellar nuclear-fusion pathway. Jet formation can involve additional disk and plasma physics, so this mechanism is a leading explanation rather than a claim that every jet has one identical cause.