7th Asia-Pacific Conference on Plasma Physics, 12-17 Nov, 2023 at Port Messe Nagoya

Global Radiation Magnetohydrodynamic Simulations of Precessing Disk arounda Spinning Black Hole
Yuta Asahina1, Ken Ohsuga1
1Center for Computational Sciences, University of Tsukuba
e-mail (speaker): asahinyt@ccs.tsukuba.ac.jp

The rotating gas around the black holes (BH) forms theaccretion disk during its accretion to the BHs. The
gravitational energy of the accreting gas is released and apart of the released energy is converted to the thermal,magnetic, and radiation energy. As a result, enormous
energy can be ejected as the strong radiation and/oroutflows from the compact object. To research thestructure and dynamics of the accretion disk, generalrelativistic (GR) radiation MHD simulations have been
performed [1,2,3]. However, the rotation axis of theaccretion disk is assumed to be aligned with the spin axisof the BH in their simulations. It is possible that therotation axis is misaligned with the BH spin axis.
When the BH spin axis is not aligned with the rotation
axis, it has been pointed out that the frame-dragging
effect can cause the precession of the accretion disk
around the BH (Lense-Thirring effect). In fact, GR MHD
simulations reproduced the disk precession [4,5,6]. This
precession might be origin of the quasi-periodic
oscillation of the luminosity and the wiggling jet.
We performed GR radiation MHD simulation of thetilted accretion disk to research effects of the precession
for high luminosity object. In the Figure 1, left panel
shows the accretion disk (blue) and outflow (orange).
The outflow is not ejected toward the BH spin axis
(white arrow), but toward the rotation axis of theaccretion disk. Near the BH, the accretion flow forms
nonaxisymmetric structure. These features are consistent
with the previous studies [4,5].
Figure 2 shows the time evolution of the polar angles(top) and azimuthal angles (bottom) of the rotation axisof the accretion disk (black), propagation direction of theradiation (red), and propagation direction of the outflow(blue). All polar angles remain almost the same as theinitial tilt angle (~30 degrees). All azimuthal angles

Figure 1 Left panel shows volume rendered density(blue) and lorentz factor (orange). The white arrowshows the BH spin axis. Right panel shows the density
distribution near the BH (white filled circle).

increase on average. This means the accretion disk,
radiation propagation direction, and outflow propagation
direction are precessing. In our simulation, the azimuthal
angle becomes 20 degrees larger than the initial
azimuthal angle in 0.5 second for the 10 solar mass BH.
Our simulation can demonstrate not only the precessionof the accretion disk and outflow but also precession of
the radiation propagation direction.
This work was supported by JSPS KAKENHI Grant
Numbers 23K03445, 21H01132, 21H04488, 18K03710,
by MEXT as a priority issue (Elucidation of thefundamental laws and evolution of the universe) to be
tackled by using post-K Computer and JICFuS, and by
MEXT as “ Program for Promoting Researches on theSupercomputer Fugaku ” (Toward a unified view of theuniverse: from large scale structures to planets)
References[1] Takahashi, H. R. et al., ApJ, 826, 23 (2016)[2] Sadowski, A. & Narayan, R., MNRAS, 456, 3929
(2016)[3] Utsumi, A. et al., ApJ, 935, 26 (2022)[4] Fragile, P. C. et al., ApJ, 668, 417 (2007)[5] Liska, M. et al., MNRAS, 474, L81 (2018)[6] Musoke, G. et al., MNRAS, 518, 1656 (2023)

Figure 2 Time evolution of the polar angles (top) andazimuthal angles (bottom) of the rotation axis (black),
radiation propagation direction (red), and outflow
propagation direction (blue).