16 September 2011 Advancements in understanding auroral ionosphere-thermosphere coupling from infrared remote sensing
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Recent discoveries from analysis of measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere- Mesosphere Energetics and Dynamics (TIMED) satellite have shown that NO(v) 5.3 um emission is the primary mechanism of dissipating solar-geomagnetic storm energy in the thermosphere. Further insight into the ionosphere-thermosphere (IT) storm-time response emerged from observations and analysis of the SABER 4.3 um channel radiances, which showed that nighttime 4.3 um emission is dominated by NO+(v) during geomagnetically disturbed conditions. Analysis of SABER NO+(v) 4.3 um emission led to major advances in the understanding of E-region ion-neutral chemistry and kinetics, such as the identification of a new source of auroral 4.3 um emission, which also provides a new context for understanding auroral infrared emission from O2(a1▵g). Surprisingly, NO+(v) 4.3 um emission is the second largest contribution to solar-geomagnetic infrared radiative response and provides a non-negligible contribution to the "natural thermostat" thought to be solely due to NO(v) 5.3 um emission. Despite these major advances, a fully physics-based understanding of the two largest sources of storm-time energy dissipation in the IT system from NO(v) and NO+(v) is lacking because of the limited information content contained in SABER's broadband infrared channel measurements. On the other hand, detailed information on the chemical-radiative excitation and loss processes for NO(v), NO+(v), and O2(a1▵g) emission is encoded in the infrared spectrum, of which SABER only provides an integral constraint. Consequently, a prototype infrared field-wide Michelson interferometer (FWMI) is currently under development to advance the understanding of IT storm-time energetics beyond the current state of knowledge. It is anticipated that progress in the developments of the FWMI technology, along with advancements in a physics-based understanding of the fundamental chemical-radiative mechanisms responsible for IT infrared emission, will play an integral role in the future planning of a rocket-borne and satellite-based Eregion science missions. In this paper, a survey of recent SABER discoveries in IT ion-neutral coupling will be given, open questions in a physics-based understanding of chemical-radiative vibration-rotation excitation and loss from important IT infrared emitters will be identified, and the FWMI instrument requirements necessary to address these open science questions will be presented.
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Christopher J. Mertens, Xiaojing Xu, Stanley J. Wellard, "Advancements in understanding auroral ionosphere-thermosphere coupling from infrared remote sensing", Proc. SPIE 8154, Infrared Remote Sensing and Instrumentation XIX, 815405 (16 September 2011); doi: 10.1117/12.895235; https://doi.org/10.1117/12.895235

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