Measurements of Thermospheric Density and Temperature from SUVI Solar Occultations

Direct observations of thermospheric neutral density, composition and temperature, and its variability provides insight into processes ranging from geomagnetic storm response to anthropogenic climate change. Furthermore, direct observations of the thermospheric state can provide indicators of space weather activity for constraining models of the thermosphere-ionosphere system. However, no such measurements are currently made in real-time for use in space weather operations, and few have been historically collected for research purposes.

We present results from a NASA Space Weather Operations to Research (SWO2R) project to develop unprecedented operational measurements of the thermospheric state using the Solar UltraViolet Imager (SUVI) onboard the GOES-R series constellation. SUVI images the Sun at extreme ultraviolet (EUV) wavelengths, with a primary objective to characterize and track the Sun's morphology as it relates to the source of geoeffective space weather. Since EUV radiation is strongly absorbed in the thermosphere, measurements of absorbed EUV irradiance can be used to probe the thermosphere via solar occultations. SUVI occulations occur around the fall and spring equinoxes and cover all global latitudes over the course of a given occultation season. The wavelengths measured by SUVI provide sufficient constraints to distinguish the two major species of the middle and upper thermosphere: N2 and O.

Presented here are measurements made of thermospheric density, temperature, and composition from approximately 150 to 300 km and how these measurements vary with EUV and geomagnetic forcing during the GOES-16 and -17 occultation seasons from 2017 to present. This data product will be integrated into the GOES processing pipeline and publicly available on the NOAA National Centers for Environmental Information (NOAA NCEI) website for occultation measurements throughout SUVI's expected operations from 2017 into the mid-2030s.