The Alfvén mission concept
Résumé
The Alfvén mission is a candidate to the 2014 ESA Call for M-class science missions. Its main scientific objective is to elucidate the universal physical processes at work in the Auroral Acceleration Region (AAR). The AAR is a unique laboratory for investigating strongly magnetized plasmas at an interface where ideal magneto-hydrodynamics does not apply. The Alfvén mission will investigate fundamental and multi-scale physical processes that govern what Nobel Prize laureate Hannes Alfvén named the Plasma Universe. The mission concept is designed to teach us where and how the particles that create the aurorae are accelerated, how they emit radiation, and to elucidate the ion heating and outflow processes which are slowly removing the Earth's atmosphere. The only way to distinguish between the models describing acceleration processes at the heart of Magnetosphere-Ionosphere (MI) coupling is to combine high-time resolution in situ measurements (as pioneered by the FAST mission), multi-point measurements (as pioneered by CLUSTER), and auroral arc imaging in one mission. Taking advantage of the existing dense network of ground based observatories the Alfvén mission will also allow a major breakthrough in our understanding of solar terrestrial relationships by providing key experimental measurements to large scale models of MI electrodynamics.