Magnetohydrodynamic flows as Newtonian-type gravitational motions

Nikolaos Spyrou 1  and Christos Tsagas 1
  • 1 Department of Astronomy, Aristoteleion University of Thessaloniki, 541.24, Thessaloniki, Greece

Abstract

We study the motion of a magnetised, highly conductive fluid within the framework of Newtonian gravity. Our analysis examines whether and under what conditions magnetohydrodynamic flows can be represented as hydrodynamic ones and then as Newtonian-type gravitational motions. In the latter case we define a generalised effective density and an effective Poisson-type potential, which include the magnetic input and determine the dynamics of the magnetised system. Introducing the dynamical equivalence of the aforementioned two representations, we use it to test mass measurements based on purely gravitational motions. We also provide the generalised Raychaudhuri equation corresponding to the aforementioned effective potential and discuss its implications for the kinematics of the fluid.

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