Scaling and asymmetry in an electromagnetically forced dipolar flow structure

Abstract

A dipolar flow structure is experimentally studied in a layer of salt solution driven by time-independent electromagnetic forcing. In particular, the response of the flow to the forcing is quantified by measuring the Reynolds number Re as a function of the Chandrasekhar number Ch (the ratio of Lorentz forces to viscous forces) and δ (the ratio of vertical to horizontal length scales of the flow domain). In agreement with theoretical predictions, two scaling regimes are found: Re∼Ch/π2 (viscous regime) and Re∼Ch1/2δ-1 (advective regime). The transition between the two regimes at Ch1/2δ∼π2 is reflected in the flow geometry in the form of an asymmetry of the dipolar flow structure. © 2011 American Physical Society.