 This asymmetry causes the electrons and ions to drift across the field, and eventually hit the walls of the torus.The solution is to shape the lines so they do not simply run around the torus, but twist around like the stripes on a barber pole or candycane.In such a field any single particle will find itself at the outside edge where it will drift one way, say up, and then as it follows its magnetic line around the torus it will find itself on the inside edge, where it will drift the other way.