The ionospheric role in the generation of small-scale auroral structures

The Ground-to-Rocket Electrons Electrodynamics Correlative Experiment (GREECE) sounding rocket mission combined high-resolution ground-based auroral imaging with high time-resolution precipitating electron measurements. The GREECE payload successfully launched from Poker Flat, Alaska on 03 March 2014 and reached an apogee of 335 km. Narrow field-of-view auroral images were taken directly under the apogee, from Venetie, AK. The small-scale auroral features at the magnetic footpoint of the rocket payload were imaged in detail. The precipitating electron distribution was measured with the Acute Precipitating Electron Spectrometer (APES) onboard the payload at 9 ms cadence. The highly structured features in the optical auroral observations are compared to the structure in the precipitating electrons. The discrepancies between the two provide an indication that much of the optical auroral structure is not contained in the precipitating electrons and therefore is generated in the ionosphere, below the spacecraft. We explore possible mechanisms for generating such structure.