Auroral distributions in the polar region viewed by the Isis 2 scanning auroral photometer are studied to examine the topology of the auroral oval. It is shown that a single continuous oval-shaped belt can be defined in which both discrete and/or diffuse auroras lie.

In addition to the above, a second belt of diffuse auroras is frequently observed in the day sector. It is less eccentric with respect to the magnetic pole than the auroral oval. This diffuse auroral belt appears to be separated from the auroral oval emission in the day sector. It probably corresponds to the mantle aurora and represents the optical component of the hard precipitation zone.