This project request funds to establish a tristatic array of all-sky imaging Fabry-Perot Doppler spectrometers in Alaska. These instruments will obtain two-dimensional maps of temperature and three-component wind vectors in Earth's upper atmosphere above approximately 100 km altitude, without requiring any a-priori assumptions about the nature of the flow. The roughly 250,000 square kilometer area of tristatic overlap will encompass all of the atmospheric volume observed by the National Science Foundation's new Poker Flat Incoherent Scatter Radar (PFISR) at F-region heights, and most of this volume in the E-region. One of the three spectrometers required for tristatic imaging is already installed and operating at Poker Flat; this project will construct the other two. Based on demonstrated performance of the existing Poker Flat instrument, the tristatic array will be able to map true three-component winds to a precision of a few meters per second across the PFISR field of view, with a spatial resolution of 50-100 km and a time resolution varying from 1 to 10 minutes. Temperatures will be measured to a typical precision of 5K. These capabilities represent an order of magnitude improvement over what was possible even as recently as five years ago. The scientific motivation for establishing this facility is to study thermospheric dynamics at short spatial and temporal scales, which have previously been inaccessible to remote sensing. According to the Navier-Stokes equations of fluid mechanics (augmented with terms describing Joule heating and ion neutral momentum coupling), narrow channels of ionospheric convection should imprint slower but otherwise similarly structured small-scale short-lived flows onto Earth's neutral thermosphere. The objective here is to test this prediction and, should it be correct, to study the nature and consequences of these small-scale flows. Further, by providing high-resolution measurements of ion number density, flow velocity, and temperature, the PFISR radar will enable quantification of the sources of energy and momentum that establish these flows. The new all-sky imaging instruments will operate in full collaboration with existing narrow-field spectrometers at Poker Flat, Fort Yukon, and Eagle, resulting in an unprecedented cluster of five FPIs viewing a common volume over northern Alaska. This activity will create a collaborative partnership involving several existing NSF-funded projects: The PFISR radar, the Toolik Field Station, and the existing narrow-field spectrometer array. Because the new instruments will use designs from La Trobe University in Australia, the project will also establish a new international collaboration, with some scope for student travel between Alaska and Australia. The design, construction, deployment and operation of these new instruments will expose participating students to a wide range of practical research skills, in addition to the usual data analysis and interpretation that are part of any observational research project.
