Imaging the Dynamic Auroral Ionosphere and Polar Ionosphere Using Incoherent Scatter Radar and All-Sky Imaging

English Abstract:

Advanced Modular Incoherent Scatter Radar (AMISR) systems have enabled multi-dimensional observations within the nightside auroral zone (PFISR) and deep within the polar cap (RISR). AMISR systems are phased-array radars capable of beam steering on a pulse-to-pulse cadence. Heinselman and Nicolls [2008] described a technique for determining the horizontal plasma flow pattern from AMISR measurements and applied this method to the estimation of E-region neutral winds. More recently, Nicolls et al., [2014] enhanced this technique to determine the electrostatic potential at F-region altitudes using a minimum curvature estimator [Cosgrove et al., 2014]. We present results of studies that have made use of the velocity field imaging applied to auroral electrodynamics in the nightside region and polar cap.

A next step forward in ISR imaging is to fold in complimentary data sources that can be used with the ISR data to improve estimates of ionospheric parameters. All-sky color imagers, collocated with ISRs, make line-of-sight measurements of the visible light emission at a variety of different wavelengths corresponding to different physical processes. Given an incident electron spectrum, forward electron transport models have been used to predict visible auroral emission and volume ionization rate, which can be indirectly observed by ISR. The all sky imagers generally provide measurements over a larger field-of-view and at much higher time cadence than ISR, thus the measurements contain useful information that can be used to enhance the spatial and temporal resolution of the 3-D electron density estimation. We present a new technique for merging photometric and ISR observations to generate improved estimates of the 3-D electron density structure in the auroral ionosphere. The improved electron density estimate can be used to determine the 3-D conductivity, and, when combined with vector electric field images, the 3-D current structure can be determined in a localized region. We discuss the applicability of this technique to monostatic ISR and the AMISR system. We use this technique to investigate currents systems and energy transfer in the auroral ionosphere, and for studies of high latitude auroral conductivity to ingestion into models.