<p>The coloured maps are analogous to those shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0169919#pone.0169919.g003" target="_blank">Fig 3</a>. That is they represent the magnitude of the net lateral force acting on particles excluding the drag associated with the induced secondary flow. The latter is represented by arrows. The outwardly-directed magnetic field gradient is canted downwards by 25 degrees relative to the horizontal to reflect experimental conditions.</p
