Abstract
Abstract. In January 1977 a new type of radar aurora experiment named STARE (Scandinavian Twin Aurora Radar Experiment) commenced operation in northern Scandinavia. The purpose of the experiment was two-fold: to make observations of the nature of radar auroras, and to contribute to the study of solar–terrestrial relationships (or space weather). The experiment was designed for automatic continuous operation, and for nearly two and a half decades it provided estimates of electron flows with good spatial coverage and resolution and good time resolution. It was a successful experiment that yielded a wealth of observations and results, pertaining to, and based on, the observed time variations of the electron flows and to the spatial flow pattern observed at any given time. This radar system inspired the creation of a similar system, SABRE (Sweden And Britain Radar Experiment), which increased the field of view towards the southwest of STARE. This system commenced operation in 1982.
Highlights
In most of the plasma regions in the space around the Earth, the electrons and ions are, to a very good approximation, moving under the influence of electric and magnetic fields in an E × B drift
It was a successful experiment that yielded a wealth of observations and results, pertaining to, and based on, the observed time variations of the electron flows and to the spatial flow pattern observed at any given time. This radar system inspired the creation of a similar system, SABRE (Sweden And Britain Radar Experiment), which increased the field of view towards the southwest of STARE
At E-region altitudes, instabilities are excited in order to create plasma waves, which can be observed with coherent radar techniques from the ground (see, for example, Nielsen (1988a), where radar principles and some properties of radar signals backscattered from the ionosphere are introduced, followed by presentation of data acquisition, coherent detection, digital sampling and data processing)
Summary
In most of the plasma regions in the space around the Earth, the electrons and ions are, to a very good approximation, moving under the influence of electric and magnetic fields in an E × B drift. The nearly horizontal, generally poleward-directed narrow antenna beams of the two radars cross over a large common “area” in the ionospheric E-region in the auroral zone In this configuration the radar wave vector is nearly perpendicular to the geomagnetic field lines, as is required for a good radar auroral backscatter signal. A surprising (or nonpredicted) result of the STARE radar measurements was the observation of toroidal and poloidal wave fluctuations of the ionospheric electron drifts These fluctuations had amplitude and phase variations across the field of view as were predicted to be associated with geomagnetic micropulsations. An important advantage of the SABRE field of view was that it allowed, in a small region, for simultaneous observations in a common backscatter volume with three antenna lobes, from Uppsala, Hankasalmi and Malvik This allowed for a more detailed analysis of the radial irregularity velocities (Nielsen et al, 1983b)
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