Optical estimation of auroral ion upflow: 2. A case study

[1] This work presents a detailed multi-instrument and modeling case study of an ion upflow event occurring over the Sondrestrom incoherent scatter radar on 17 February 2001. This case study is used to demonstrate the effectiveness of a previously developed optical estimator of ion upflow. The optical estimator of ion upflow is applied in a two step process: (1) near-infrared (NIR) optical observations in the 700–850 nm wavelength range are inverted to reconstruct the energy distribution of precipitating electrons then (2) the reconstructed precipitation is applied to a combined fluid-kinetic model of the ionosphere (TRANSCAR) to estimate the plasma response to the auroral particles. Plasma parameters estimated by this procedure are compared with plasma parameters derived from incoherent scatter radar data recorded during the event and are shown to be in reasonably good agreement. However, this study highlights an important limitation of the estimation technique, the lack of a direct measure of the ambient ionospheric state (nighttime plasma density). Means for addressing this limitation are discussed and may eventually allow for estimation of ionospheric state parameters under certain conditions by using optical sensors.