A three year investigation is proposed to address the evolution of thermospherically disturbed regions produced during geomagnetic storms and their correlation with negative ionospheric storms. The proposal is motivated by the successful outcome of a two year investigation by the PI under a NASA contract to derive thermospheric composition images on the dayside from DE-1 FUV imaging data. The images are in the form of O/N2, the column abundance of O relative to N2 referenced to a fixed depth in the latter species. The work demonstrated that the radiance data can be converted to O/N2 with sufficient accuracy to effectively quantify the structure and intensity of regions of reduced O/N2 (O depletion patches [ODPs]) arising from intense heating at high latitudes during geomagnetic storms. O/N2 images have been produced from various storm-time data showing reductions in O/N2 by more than a factor of two over extended mid-latitude regions. In the current work, the focus will be on first-principles ionospheric modeling to understand the behavior of the observed ionosphere within thermospherically disturbed mid-latitude regions. A key aspect of the modeling will be to reproduce the measure-ments inside and adjacent of O depleted regions within constraints imposed by DE-1-based O/N2. Whereas a key goal of the proposed NASA work will be correlating data with data (DE-based O/N2 with ionospheric measurements), here a key goal will be to better understand the neutral density behavior at E-region heights within O depleted regions through the stated modeling effort. The approach is to attempt to replicate ionospheric observations during O depletion events by modifying the empirical models of neutral densities and winds used in the ionospheric models. That is, an attempt will be made to deduce something about thermospheric structure in O depletion events by working backwards from the observed effects of these events on ionospheric structure. The long range goal is to be able to use satellite images of O/N2 to map out regions likely to be experiencing negative ionospheric storm effects.
