The Polar Cusp and its Ionospheric footprint : Dynamics and Transients

Abstract: The magnetopause, the boundary layer between the solar wind and the Earth’s magnetosphere, is not closed as we have long thought. Transfers of energy, particles and momentum from the solar wind to the magnetosphere actually take place. In the Earth’s magnetosphere, the polar cusps are two key regions where the solar wind particles have direct access to the magnetosphere and the polar ionosphere. The ionospheric footprint of the polar cusp is highly dynamic because its location and behavior depend directly on the external conditions (interplanetary magnetic field and solar wind pressure). The cusp dynamics has been studied by means of ground-based and satellite-borne instrumentation. The theory of magnetic reconnection has been successful in explaining entry of solar wind particles into the magnetosphere. Observations indicate that the reconnection process is not steady but rather sporadic or pulsed. The consequences of transient injections of solar wind particles into the dayside high-latitude ionosphere and the associated strong convection electric fields are observed, modeled and discussed.