Techniques for producing and manipulating magnetic fields. The techniques employ the mutual repulsion of magnetic fields to create uniform magnetic fields and to manipulate the uniform magnetic fields. The uniform magnetic field is created between two planar magnets. The planar magnets have cores which describe a closed curve. Like poles of the electromagnets are connected by the cores. When the electromagnets are activated, repulsion between the magnetic fields generated by the electromagnets creates a magnetic field which extends above and below the planes of the planar magnets. If the planar magnets are positioned parallel to each other and aligned so that the magnetic fields generated by the planar magnets repel each other in the space between the planar magnets, the repulsion between the fields generates a resultant field. When the distance between the planar magnets is approximately the diameter of the closed curve, the resultant field is uniform over a considerable volume of the space between the planar magnets. The uniform field may be manipulated by varying the magnitude and direction of the current provided to the electromagnets. Depending on the number and positions of the electromagnets and how power is supplied to them, the uniform field may be rotated, tilted in the horizontal and/or vertical planes, warped in the horizontal and/or vertical planes, and given gradients in the horizontal and/or vertical planes. The planar magnets may be fitted around the chambers of reactors such as those used for MERIE and the uniform field may be used to manipulate the plasma in the reactor chamber.