Nowcasting the state of the magnetosphere Original Research Article

Because of the adverse effects of space weather on manmade systems in space and on the ground, it is imperative that techniques be developed to provide an assessment of the state of the magnetosphere in near real time. In this paper we demonstrate a technique which is based on the premise that large rapid perturbations of the magnetosphere-ionosphere system are a consequence of the sudden release of energy stored in the magnetotail. We use a ground based array of magnetometers to establish the high latitude edge of the auroral oval and use this measurement as a proxy for the equatorward edge of the polar cap. A measure of the size of the polar cap is then used to predict the position and intensity of substorm expansive phase disturbances.