Presentation #115.19 in the session Multi-Messenger Astrophysics.
Within the framework of General Relativity, astrophysical black holes are fully characterised by their mass, electric charge, and angular momentum (spin). The interplay between the charge and spin is not intuitive and a small (non-zero) value of charge should not be ignored in non-stationary systems. Efficient acceleration up to ultra-high energies can occur due to frame-dragging effects near charged, spinning black holes embedded in magnetic fields organized on the event horizon scale. We employ appropriate mathematical framework to describe these effects and we provide examples how these can be employed in the context of accreting supermassive black holes in cores of galaxies.