Scaling and asymmetry in an electromagnetically forced dipolar flow structure

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 delta (the ratio of vertical to horizontal length scales of the flow domain). In agreement with theoretical predictions, two scaling regimes are found: Re similar to Ch/pi(2) (viscous regime) and Re similar to Ch(1/2)delta(-1) (advective regime). The transition between the two regimes at Ch(1/2)delta similar to pi(2) is reflected in the flow geometry in the form of an asymmetry of the dipolar flow structure.