Two methods to forecast auroral displays

This work compares the methods by Starkov (1994a) and Zhang & Paxton (2008), that calculate the size and location of the auroral ovals as a function of planetary Kp index. The ovals are mapped in position and time onto a solar illuminated surface model of the Earth. It displays both the night- and dayside together with the location of the twilight zone as Earth rotates under the ovals. The graphical display serves as a tool to forecast auroral activity based on the predicted value of the Kp index. The forecast is installed as a service at http://kho.unis.no/. The Zhang & Paxton (2008) ovals are wider in latitude than the Starkov (1994a) ovals. The nightside model ovals coincide fairly well in shape for low to normal auroral conditions. The equatorward border of the diffuse aurora is well defined by both methods on the nightside for Kp ≤ 7. The dayside needs further studies in order to conclude.