Remote-Sensing Magnetotail Dynamics from Low Earth Orbit with CINEMA

Low-altitude measurements provide a unique vantage point for studying processes occurring in the magnetosphere, taking advantage of the fact that energetic particles move quickly along magnetic field lines. Low-Earth-orbiting (LEO) polar satellites can sample a vast volume of space as they rapidly traverse magnetic field lines, obtaining a radial snapshot of the entire magnetotail in minutes. CINEMA (Cross-scale INvestigation of Earth's Magnetotail and Aurora) is a NASA Small Explorer mission concept with the overarching goal to understand the role of plasma sheet structure and evolution in Earth’s multiscale magnetospheric convection cycle. How the magnetotail maintains steady convection, and when and how it decides to explosively release stored energy, are major unsolved mysteries of space physics. CINEMA’s nine satellites in LEO polar orbits each carry an on-board imager, particle sensors, and magnetometers, and quickly traverse the low-altitude footprint of the magnetotail, capturing its evolution at different scales. CINEMA obtains information about the structure of the magnetotail remotely through its imprint on particle pitch-angle distributions, providing an unprecedented view of particle isotropy boundaries. Mesoscale aurora and bursty energetic particle precipitation serve as tracers of specific mesoscale and kinetic-scale dynamics. Field-aligned currents (FACs) that connect the magnetotail to the ionosphere are sensed by measuring magnetic field variations at each satellite. Together, these observations reveal the physics underlying multiscale magnetotail convection.