Vorticity generation in accretion disks around Schwarzschild and Kerr black holes is investigated in the context of magnetofluid dynamics derived for both General Relativity (GR) and modified gravity formulations. In both cases, the Kerr geometry leads to a "stronger" generation of vorticity than its Schwarzschild counterpart. Of the two principal sources, the relativistic drive peaks near the innermost stable circular orbit (isco), whereas the baroclinic drive dominates at larger distances. Consequences of this new relativistic vorticity source are discussed in several astrophysical settings. © 2015 American Physical Society.

Bhattacharjee C.

Das R.

Mahajan S.M.

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Physical Review D - Particles, Fields, Gravitation and Cosmology

Using the magnetofluid unification framework, we show that the accretion disk plasma (embedded in the background geometry of a black hole) can relax to a class of states known as the Beltrami-Bernoulli (BB) equilibria. Modeling the disk plasma as a Hall magnetohydrodynamics (MHD) system, we find that the space-time curvature can significantly alter the magnetic (velocity) decay rates as we move away from the compact object; the velocity profiles in BB states, for example, deviate substantially from the predicted corresponding geodesic velocity profiles. These departures imply a rich interplay of plasma dynamics and general relativity revealed by examining the corresponding Bernoulli condition representing "homogeneity" of total energy. The relaxed states have their origin in the constraints provided by the two helicity invariants of Hall MHD. These helicities conspire to introduce an oscillatory length scale into the system that is strongly influenced by relativistic and thermal effects. © 2015 American Physical Society.

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Beltrami state in black-hole accretion disk: A magnetofluid approach

Physical Review D

Magnetofluid dynamics in curved spacetime

Living Reviews in Relativity

Foundations of Black Hole Accretion Disk Theory

Astronomy & Astrophysics

Accretion disks around black holes in modified strong gravity

The Astrophysical Journal

THE LARGE-SCALE MAGNETIC FIELDS OF THIN ACCRETION DISKS

A PARAMETER STUDY FOR BAROCLINIC VORTEX AMPLIFICATION

Novel mechanism for vorticity generation in black-hole accretion disks