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Accretion discs properties should deviate from standard theory when magneticpressure exceeds the thermal pressure. To quantify these deviations, we presenta systematic study of the dynamical properties of magnetically arrested discs(MADs), the most magnetized type of accretion disc. Using an artificial coolingfunction to regulate the gas temperature, we study MADs of three differentthermal thicknesses, $h_\mathrm{th}/r=0.3, 0.1$ and $0.03$. We find that theradial structure of the disc is never mostly supported by the magnetic field.In fact, thin MADs are very near Keplerian. However, as discs gets colder, theybecome more magnetized and the largest deviations from standard theory appearin our thinnest disc with $h_\mathrm{th}/r=0.03$. In this case, the disc ismuch more extended vertically and much less dense than in standard theorybecause of vertical support from the turbulent magnetic pressure andwind-driven angular momentum transport that enhances the inflow speed. The thindisc also dissipates a lot of thermal energy outside of $z/r = \pm 0.03$ and asignificant fraction of this dissipation happens in mildly relativistic winds.The enhanced dissipation in low-density regions could possibly feed coronae inX-ray binaries (XRBs) and active galactic nuclei (AGN). Wind-driven accretionwill also impact the dynamical evolution of accretion discs and could provide amechanism to explain the rapid evolution of changing-look AGN and the secularevolution of XRBs. Finally, our MAD winds have terminal velocities and massloss rates in good agreement with the properties of ultra-fast outflowsobserved in AGN.

Magnetic support, wind-driven accretion, coronal heating, and fast outflows in a thin magnetically arrested disc