Abstract
Abstract. The work presents a data-model synthesis examining the response of the auroral F-region ion temperature, composition, and density to short time scale (<1 min) electric field disturbances associated with auroral arcs. Ion temperature profiles recorded by the Sondrestrom incoherent scatter radar (ISR) are critically analyzed with the aid of theoretical calculations to infer ion composition variability. The analyses presented include a partial accounting for the effects of neutral winds on frictional heating and show promise as the groundwork for future attempts to address ion temperature-mass ambiguities in short-integration ISR data sets. Results indicate that large NO+ enchancements in the F-region can occur in as little as 20 s in response to impulsive changes in ion frictional heating. Enhancements in molecular ion density result in recombination and a depletion in plasma, which is shown to occur on time scales of several minutes. This depletion process, thus, appears to be of comparable importance to electrodynamic evacuation processes in producing auroral arc-related plasma depletions. Furthermore, the potential of ionospheric composition in regulating the amounts and types of ions supplied to the magnetosphere is outlined.
Highlights
Electric fields are a ubiquitous feature of the high latitude ionosphere
Modeling and Sondrestrom incoherent scatter radar (ISR) evidence of F-region ion composition variability on time scales of less than one minute have been presented in this work
In this work composition variability is inferred through a novel synthesis of apparent ion temperature inversion measurements and careful data-model comparisons
Summary
Electric fields are a ubiquitous feature of the high latitude ionosphere. Auroral arcs, in particular, are associated with strong perpendicular electric fields (Marklund, 1984; Johnson et al, 1998), often localized at arc boundaries (e.g. Evans et al, 1977; Opgenoorth et al, 1990). Lathuillere and Kofman, 2006) Methods to address these problems rely on specifying either the electron temperature (Kelly and Wickwar, 1981) or ion temperature (Haggstrom and Collis, 1990) via a model or assumption and fitting IS spectra for composition. This paper focusses on the response of high-latitude Fregion ion composition to dynamic (short time scale) electric field disturbances. Artifacts in ion temperature profiles have been noted before as being indicative of a wrong ion composition assumption in the ISR fitter (Shibata et al, 2000; Oyama et al, 2004), but this research undertakes a critical data-model comparison of the temperature profiles. In the analysis presented careful attention is given to the effects of horizontal neutral winds on temperature profiles and ion composition
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