CEDAR: A Study of the Coupled Thermosphere, Exosphere and Hot Oxygen Geocorona

Scientific Solutions Incorporated, North Chelmsford MA

Investigators

Abstract

This project investigates non-thermal populations of neutral atomic hydrogen, metastable helium, and oxygen ions that are the manifestation of ion-neutral coupling between the thermosphere, ionosphere, and exosphere. Fabry-Perot interferometers (FPI) at the Arecibo Observatory are used to directly sample the velocity distributions of O+, metastable He, and H above the F-region peak, using measurement and analyses of the infrared (IR) 732 nm, 108.3 nm, and optical 656.3 nm airglow emission line profiles respectively. The 430 MHz incoherent scatter radar (ISR) is operated simultaneously, providing the thermal, compositional, and dynamic state of the coupled topside ionosphere. The observations will help characterize thermal and dynamical coupling between the few neutral and ions species populating the upper atmosphere. Resolution of persistent uncertainties, including energy balance between the thermosphere and topside ionosphere, and the atmospheric escape of light gases, demands a quantitative assessment of the role of non-thermal populations in the structure and dynamics of the coupled regions. The data will be used to infer the abundances and velocity distributions of non-equilibrium particles between 300 and 1000 km altitude and consequently characterizes the various physical, chemical, and dynamic processes that the coupled species undergo. Questions that will be addressed by quantification of energetic populations include a controversial heat-balance discrepancy between F-region temperature and neutral O density calculated by semi-empirical models. The temperature sensitivity of ion-neutral interaction may contribute to sustenance of the nighttime F-region, which is only loosely, ascribed to downward transport from the plasmasphere at night. A central objective of this project is a long-overdue upgrade of the Arecibo Optical Laboratory. These upgrades benefit and invigorate research using the nested instrumentation at Arecibo. Space weather and global change research are broadly impacted by improved modeling based on well constrained H and H+ topside abundances.