PI: Joshua Stanway

Project dp340, which started in April 2025, investigates accretion disks around supermassive black holes, where the angular momentum of the disk and black hole are misaligned. This represents a more general case of accretion, as infalling material is unaware of the black hole’s spin. Our study focuses on exploring how the magnitude and sign of black hole spin can influence the evolution of a misaligned accretion disk.

To carry out this investigation we produced nineteen, three-dimensional general relativistic magnetohydrodynamic simulations with the code KHARMA, sixteen of which vary the black hole spin, and initial accretion disk misalignment. A further three were produced with a single black hole spin, but a weaker magnetic field, for an additional study. We find the geometry of the disk, and the jet, are significantly between prograde (co-rotating disk) and retrograde (counter rotating disk) simulations, for all initial disk misalignments. In prograde simulations, sufficient magnetic flux builds up at the event horizon, launching a powerful jet, torquing the disk into alignment. Retrograde simulations, however, cannot form a sufficiently powerful jet, and thus, the disk and jet, stay misaligned, as seen in the bottom two rows of Figure 1.

Figure 1: Time averaged logarithmic density of twelve misaligned disk simulations, including the first highly misaligned retrograde simulations. Prograde simulations form powerful jets, the large low density regions enclosed by the black contours. Retrograde models have much more turbulent, and intermittent jets, which cannot align the inner accretion disk. The results of this study are being prepared for publication.