Five Years of Stereo Magnetospheric Imaging by TWINS

摘要: Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS) is the first stereoscopic magnetospheric imager. TWINS a NASA Explorer Mission of Opportunity performing simultaneous energetic neutral atom (ENA) imaging from two widely-separated Molniya orbits on different spacecraft, and providing nearly continuous coverage ENA emissions. The imagers observe neutrals produced global ion populations, over broad energy range (1–100 keV/u) with high angular (4∘×4∘) time (about 1-minute) resolution. distinguishes hydrogen ENAs oxygen ENAs. Each spacecraft also carries Lyman-α geocoronal imager to monitor cold exospheric atoms that produce ions via charge exchange. Complementing are detectors measure local charged particle environment around spacecraft. During its five years science operations, has discovered new properties geospace plasmas neutrals, fostered understanding causal relationships, confirmed theories predictions based in situ data, yielded key insights needed improve models. Analysis modeling data have: (1) obtained (main phase through recovery) spectra, (2) revealed previously unknown local-time dependence pitch angle, (3) developed quantitative determination fluxes low altitude (4) determined dynamic connections between angle precipitation, (5) confirmed precipitating temperature, (6) imaged heating magnetosphere, (7) explained why ring current survives longer into recovery than hydrogen, (8) revealed density features their influence upon decay rates. Over next several solar cycle, observations three-dimensional (3D) dynamics, composition, origins destinies crucial capture system-level view full geomagnetic activity conditions.