title: Beltrami state in black-hole accretion disk: A magnetofluid approach.
abstract: 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.
authors.affiliation: Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA.|Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Chinmoy
authors.initials: C
authors.lastname: Bhattacharjee
authors.affiliation: Department of Physical and Applied Sciences, Madonna University, Livonia, Michigan 48150, USA.
authors.forename: Rupam
authors.initials: R
authors.lastname: Das
authors.affiliation: Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA.|Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Stark
authors.affiliation: Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA.|Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.|Shiv Nadar University, NH91, Tehsil Dadri, Gautam Buddha Nagar, Uttar Pradesh, 201 314, India.
authors.forename: S M
authors.initials: SM
authors.lastname: Mahajan