Magnetic surfaces in the reversed-field geometry

Field reversal does not ensure closure of the reversed-field geometry. The closure is critically dependent on the structure of the field , which breaks the toroidal symmetry, no matter how small it may be. However, the plasma diamagnetic current is shown to establish a spatial scale for the variation of which is λ ≅ a/(β 1 ) 1/2 , with a the plasma radius and β 1 the plasma beta relative to the field.