Kilogauss Magnetic Fields Near Black Hole Horizons – Mikhail Lisakov

The launching of ultra-relativistic jets in active galactic nuclei (AGN) is thought to be driven by a combination of black hole spin, accretion dynamics, and strong magnetic fields. Until recently, direct measurements of magnetic field strength near supermassive black holes were scarce. The Event Horizon Telescope (EHT) has provided key constraints on magnetic fields in the vicinity of M87* and Sgr A*, revealing values of several tens of Gauss.

For powerful quasars such as 3C 273 and NRAO 530, where direct imaging of the central engine remains beyond current capabilities, we have used high-resolution VLBI polarimetric observations at multiple frequencies to infer the magnetic field strength indirectly through its effects on jet opacity and polarization. Our analysis reveals magnetic field strengths of up to 30,000 G in NRAO 530, localized at five gravitational radii of the central black hole.

Magnetic fields exceeding 10^5 G pose a serious challenge to current models of accretion flows and may imply unconventional physical conditions or even alternative descriptions of the central compact object. I will present a recently started project aiming to measure magnetic fields near a dozen supermassive black holes to test this hypothesis.