Supertransient Magnetohydrodynamic Turbulence in Keplerian Shear Flows: The role of the Hall Effect

Abstract

Space and astrophysical plasmas are frequently found in the regime of differential rotation, where the presence of a magnetic field can result in the magnetorotational instability, directly responsible for important phenomena such as turbulent angular momentum transport in accretion disks. In the absence of an imposed magnetic field, a nonlinear dynamo is necessary for this transport mechanism to take place. In protoplanetary disks there are regions with high density and very low temperatures, which are two necessary conditions for the Hall effect to operate, affecting the development of the dynamo and the associated turbulence. In this work we perform local magnetohydrodynamic (MHD) simulations to study transition to weak turbulence in Keplerian shear flows with Hall effect. The Hall effect is shown to lead the system to long-lived turbulent transients whose decay time follows an exponential dependence on the magnetic Reynolds number and the Hall parameter.