Using high-resolution general relativistic magnetohydrodynamic (GRMHD)
simulations, we investigate accretion flows around spinning black holes and
identify three distinct accretion states. Our results naturally explain some of
the complex phenomenology observed across the black hole mass spectrum. The
magnetically arrested disk (MAD) state, characterized by strong magnetic fields
(plasma-$\beta << 1$), exhibits powerful jets (of power $\sim10^{39}$ erg s$^{-1}$), highly variable accretion, and significant sub-Keplerian motion. On the other hand, weakly magnetized disks (plasma-$\beta >> 1$), known as the
standard and normal evolution (SANE) state, show steady accretion with
primarily thermal winds. An intermediate state bridges the gap between MAD and
SANE regimes, with moderate magnetic support (plasma-$\beta \sim 1$) producing
mixed outflow morphologies and complex variability. This unified framework
explains the extreme variability of GRS 1915+105, the steady jets of Cyg X-1,
and the unusually high luminosities (even super-Eddington based on stellar mass
black hole) of HLX-1 without requiring super-Eddington mass accretion rates.
Our simulations reveal a hierarchy of timescales that explain the rich variety
of variability patterns, with magnetic processes driving transitions between
states. Comparing two with three dimensional simulations demonstrates that
while quantitative details differ, the qualitative features distinguishing
different accretion states remain robust. The outflow power and variability
follow a fundamental scaling relation with mass determined by the magnetic
field configuration, demonstrating how similar accretion physics operates from
stellar-mass X-ray binaries (XRBs) to intermediate mass black hole sources.
This could be extrapolated further to supermassive black holes.

Cet article explore les excursions dans le temps et leurs implications.

Télécharger PDF: