The investigators will study the role of thermospheric composition in producing changes in the F-region ionosphere. The mechanism for producing an increase in the O+ density in the F-region (a positive ionospheric storm) or a decrease (a negative ionospheric storm) is not well understood. Much of the information of thermosphere and ionosphere is either confined to vertical profiles at a particular point or column integrated quantities. For this study, the investigators will use vertical profiles of the topside ionosphere, simultaneous common-volume determinations of neutral composition, and in situ measurements to test understanding of the processes that determine F region electron density. Simple model calculations will be used to guide the investigation and aid in the interpretation of the results. The ground-based and space-based measurements will be obtained for several carefully selected events. By combining the measurements with the output of computation models, the investigators will the understanding of the mechanisms that create stormtime disturbances in thermospheric composition and ionospheric plasma density in low-middle latitude F region. The results will be valuable in improving the prediction of the extent and severity of space weather storm impacts to society. Two female researchers at the Korea Astronomy and Space science Institute (KASI) will participate in the project. KASI manages a newly created national space weather program in Korea. As well as teaching and training young researchers from an under-represented gender and ethnic background, this project promotes essential international collaboration in the investigation of global space weather phenomena.
In this project, we investigated the behavior of the disturbances in the ionosphere and thermosphere during geomagnetic storms. The key outcomes of this project are (1) the different behavior of O and N2 disturbances, (2) the contamination of the O/N2 ratio derived from optical observations, and (3) the importance of spatial components in the evolution of the ionospheric disturbances observed by satellites. Our results showed the different evolution of the O and N2 disturbances depending on altitude and latitude. The O/N2 ratio disturbance was dominated by the change in N2 in the region where the O/N2 ratio was reduced, whereas, it was dominated by the change in O in the region where the O/N2 ratio was enhanced. In middle latitudes, the contamination of the O/N2 ratio by the OI 135.6 nm emission caused by the radiative recombination of the oxygen ion was not ignorable. Therefore, knowledge of the magnitude of the contamination is necessary in order to have an accurate assement of the storm-time O/N2 ratio increase at low- to mid- latitudes during large storm events. The sever enhancements of the oxygen ion denisty in middle latitudes occurred in the dayside longitude during the main phase of storms. The region where the O/N2 ratio contamination occurred corresponded to the region where the enhancement of the oxygen ion density was significant. The enhancements of the oxygen ion density persisted for several hours and produced steep plasma density gradient at the subauroral region. The ionospheric disturbances seen by satellites appeared to evolve with time following the storm phase, but we showed that the significant portion of the apparant temporal evolution of the ionospheric disturbances was associated with the corotation of the disturbances with the Earth. Our results will provide a valuable reference to the researchers who investigate the ionospheric and thermospheric disturbances using optical observations and satellite data.
