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Prevalent around luminous accreting black holes, thin discs are challengingto resolve in numerical simulations. When the disc and black hole angularmomentum vectors are misaligned, the challenge becomes extreme, requiringadaptive meshes to follow the disc proper as it moves through the computationalgrid. With our new high-performance general relativistic magnetohydrodynamic(GRMHD) code H-AMR we have simulated the thinnest accretion disc to date, ofaspect ratio H/R~0.03, around a rapidly spinning (a=0.9375) black hole, using acooling function. Initially tilted at 10 degrees, the disc warps inside r~5 r_ginto alignment with the black hole, where r_g is the gravitational radius. Thisis the first demonstration of Bardeen-Petterson alignment in MHD with viscosityself-consistently generated by magnetized turbulence. The disc develops alow-density high-viscosity (alpha_eff ~ 1.0) magnetic-pressure--dominated innerregion at r<25 r_g that rapidly empties itself into the black hole. This innerregion may in reality, due to thermal decoupling of ions and electrons,evaporate into a radiatively inefficient accretion flow if, as we propose, thecooling time exceeds the accretion time set by the order unity effectiveviscosity. We furthermore find the unexpected result that even our very thindisc can sustain large-scale vertical magnetic flux on the black hole, whichlaunches powerful relativistic jets that carry 20-50% of the accretion poweralong the angular momentum vector of the outer tilted disc, providing apotential explanation for the origin of jets in radio-loud quasars.

Bardeen-Petterson Alignment, Jets and Magnetic Truncation in GRMHD Simulations of Tilted Thin Accretion Discs