The Energetic Neutral Atom (ENA) imager records the energetic ion content of the ring current and plasma sheet. ENA is a foil-based Time-of-Flight (ToF) energetic neutral atom imager that measures the neutral particles produced when energetic ions charge exchange within the magnetosphere, enabling investigations into how magnetospheric regions respond to solar wind drivers,
as well as how the magnetospheric system can feedback on itself. ENA employs the same basic principles used in the INCA (Cassini), HENA (IMAGE), ULEIS (ACE), and JENI (JUICE) sensors.
ENA employs thin foil-based imaging microchannel plates (MCP), each backed by a 2D time delay anode, and ToF by pulse-height analysis. The fine collimation of ENA allows for a high spatial resolution of 2° (1 RE from the orbit of STORM) for ions above 30 keV/nuc. The large 60° x 68° field-of-view of ENA allows for simultaneous images of both the ring current and plasma sheet. Additionally, the ENA energy range (2 – 300 keV) allows for the retrieval of the total ring current pressure and for capturing the plasma sheet down to the thermal peak.