We present SMILE (Solar wind Magnetosphere Ionosphere Link Explorer, http://www.mssl.ucl.ac.uk/SMILE/), a concept space mission which aims to measure Earth's global system responses to solar wind and geomagnetic variations, and to shed light on many issues relating to solar-terrestrial relationships and space weather. This concept mission has been put forward in response to the European Space Agency and Chinese Academy of Sciences joint call for a small-size space mission. A team of scientists and engineers from the UK, China, Canada, Finland and the US are collaborating to make SMILE a reality.
Operating from a high inclination high apogee orbit that routinely enters the solar wind, SMILE will investigate the dynamic response of the Earth's magnetosphere to varying solar wind conditions in a unique manner, never attempted before: it will combine soft X-ray images of the density structures at the Earth's magnetopause and magnetospheric cusps with simultaneous UV images of the auroral displays associated with particle precipitation into the northern polar ionosphere. SMILE will carry an ion analyser and a magnetometer to monitor solar wind and magnetosheath conditions, thereby enabling simultaneous comparisons of the X-ray and UV images with the upstream driving conditions.
With its well integrated payload SMILE will provide answers to many open questions in solar-terrestrial relationships, and hence space weather, in a thoroughly novel way. In particular, for the first time we will be able to trace and link magnetopause and cusp interaction processes to their ionospheric consequences and solar wind drivers during the course of geomagnetic storms and substorms.