CEDAR: Dynamics of the Neutral Upper Atmosphere and Coupling to the Topside Ionosphere

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This is a 5-year project to investigate observationally the dynamic and chemical coupling of the neutral upper thermosphere to the exosphere, to the ionosphere, and to the lower thermosphere using passive optical and incoherent scatter radar (ISR) techniques. The project builds on upgraded instrumentation and advanced experimental optical and infrared techniques that were developed under the proposing team's previous CEDAR grant. Three recently upgraded Fabry-Perot Interferometers (FPIs) at Arecibo Observatory will be used to study nightglow emissions from O, H, He. The main science goal is to quantify the nighttime neutral transport from the lower thermosphere to the exosphere using the three high resolution FPIs to measure neutral temperatures and winds. Simultaneous ISR measurements of ion densities, ion drifts, ion temperatures, and electron temperature in the topside ionosphere will also be obtained. This allows for the investigation of the dynamic thermal and chemical coupling between the major neutral and ionic species in the upper thermosphere, exosphere and topside ionosphere. Specifically, the three FPIs and two photometers will be operated in campaign-mode, during four new moon periods each year of the five-year program, which carries this observational research effort through the next solar maximum. Two of these campaigns are scheduled in the fall and winter each year, a third in the spring, and a fourth near September equinox. Based on this, a number of specific outstanding science questions will be addressed, including: 1) Is there a persistent population of hot oxygen in the upper thermosphere and topside ionosphere? 2) Is the enhancement of tropospheric methane abundance during the second half of the 20th century altering the composition at the top of atmosphere? 3) How do neutral winds vary with altitude in the thermosphere and exosphere? 4) What is magnitude and semi-diurnal behavior of vertical neutral winds near the F2-peak? The project has significant broader impacts. The measurements and scientific findings that will result from the project are relevant both to space weather and climate research. The project will support the early career development of a Hispanic female scientist as well as two other female professionals and also will support the infrastructure at Arecibo Observatory through the further development of the current instrumentation there and through extensive collaboration with the observatory personnel.