New Perspectives on Small-Scale and Rapidly Varying Auroral Structures from CASSIOPE e-POP Fast Auroral Imager (FAI) Observations

English Abstract:

The Fast Auroral Imager (FAI) on the CASSIOPE Enhanced Outflow Probe (e-POP) consists of two CCD cameras, which measure the atomic oxygen emission at 630 nm and prompt auroral emissions in the 650 to 1100 nm range, respectively, using a fast lens system and high quantum-efficiency CCDs to achieve high sensitivity, and a common 26 degree field-of-view to provide nighttime images of about 650 km diameter at apogee (1500 km). The FAI is capable of operating in four viewing modes: nadir viewing, for imaging over a large latitude range; Earth-target viewing, for pointing at an emission target of fixed altitude, latitude and longitude; limb viewing, for measurement of altitude profiles; and inertial pointing; for imaging of an inertial target such as a star field. The near infrared camera provides up to two images of 0.1 sec exposure per second, with a spatial resolution of a few km in the nadir viewing mode, while the 630-nm camera provides one image of 0.5 sec exposure every 30 seconds. The four viewing modes make possible the observations of a variety of auroral and airglow phenomena, such as transpolar arcs and drifting polar patches, rapidly varying and small-scale auroral structures in the auroral oval, and detached and stable auroral red (SAR) arcs as well as airglows at lower latitudes. We will focus on new features in the observed data and the resulting new perspectives on auroral structures in the context of high-resolution studies of the ionosphere.