Extreme magnetic fields around black holes

Koushik Chatterjee (Harvard University)

February 15, 2023

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Abstract: Recent results of the event horizon-scale images of M87* and Sagittarius A* from the Event Horizon Telescope Collaboration show that strong magnetic fields are likely present around the central black holes in these sources. Magnetically arrested disks, the end stage of magnetic flux saturation around black holes, are especially rich in horizon-scale physics due to the presence of powerful jets and magnetic flux eruptions that provide significant feedback on the accretion mechanism. I will provide an overview of our current knowledge about the magnetic field evolution in numerical simulations of accreting black holes, and on my recent work on time variability in black hole images during high-energy flare events, which are often seen in X-ray lightcurves of Sagittarius A*.