Magnetospheric Auroral Asymmetry eXplorer: observing the auroral to uncover how energy flows in space - A Phase A SMEX Mission concept

The Magnetospheric Auroral Asymmetry Explorer (MAAX) mission concept makes a significant leap in determining how magnetosphere-ionosphere electrodynamic coupling regulates multi-scale energy flow through the near-Earth space environment. Recently selected for a competitive Phase A mission concept study for NASA's Heliophysics Small Explorer program, MAAX accomplishes this by:

• Understanding how seasons and tilt of the magnetic field regulate energy flow from the solar wind through the geospace system.
• Discovering how the auroral background conductance governs the formation, evolution, and interhemispheric asymmetries of nightside meso-scale auroral features.
• Determining how the time-dependent magnetospheric energy flow controls multi-scale auroral dynamics.

The solar wind energy enters the magnetosphere mainly through dayside reconnection. It is stored in the magnetospheric lobes, released in the tail, converted to plasma thermal and kinetic energies. The dynamic processes in the nightside magnetosphere map from the magnetosphere to the ionosphere, resulting in auroral structures. Observations of the aurora have been used as a window to probe and understand these dynamics even beyond the Earth system. The magnetic field lines in which the aurora occurs thread through both hemispheres. Traditionally, auroral observations from one hemisphere are assumed to be conjugate, while limited observations suggest this may not always be applicable. Thus, we can only understand some of the processes that control energy flow through the system from one hemisphere. With observations in both hemispheres, we gain a deeper understanding of the dynamics of this integrated system. MAAX comprises two observatories in circular polar orbits at 20,850 km altitude to view the two auroral ovals. Each satellite carries a high-heritage UV imager that operates poleward of +/-35° latitude. For the mission's 1st year, the observatories are spaced at 90° to allow continuous coverage of each oval with a 6-hour duty cycle. This phase also provides intervals in which both view the same hemisphere or the exact longitude but different hemispheres. For the 2nd year of the mission, the observatories are spaced at 180° to have simultaneous complete viewing of both auroral ovals with a 4.5 hr/1.5 hr on/off duty cycle. Discussed here are the scientific motivations of the mission concepts.