HAO Colloquium - Liying Qian, HAO

Solar Irradiance Effects on the Upper Atmosphere on Time Scales from Minutes to Multi-Decadal 

The upper atmosphere (thermosphere and ionosphere) is a coupled system that is predominantly driven by external forcing. The external forcing consists of solar irradiance, the coupling between the magnetosphere and the upper atmosphere, and the coupling between the mesosphere and the upper atmosphere. The external forcing from solar irradiance, the magnetosphere, and the lower atmopshere, together with internal processes within the system, drive complex temporal and spatial variabilities. In this presentation, I will address upper atmosphere variability driven by solar irradiance, on time scales from minutes to multi-decadal, using model simulations and datasets. Solar irradiance is the primary energy input to the upper atmosphere. The thermosphere absorbs solar irradiance in the soft X-ray Ultra-Violet (XUV, 1–30 nm), Extreme Ultra-Violet (EUV, 30–120 nm), and Far Ultra-Violet (FUV, 120–200 nm). Solar irradiance ionizes, dissociates, and excites thermospheric constituents, creates the ionosphere, and heats the thermosphere. The time scales that will be addressed include minutes to hours due to solar flares, diurnal, solar-rotational, annual/semiannual, solar-cycle, and multi-decadal. The models used are the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) and Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCM-X). Solar irradiance is provided by the Flare Irradiance Spectral Model (FISM) and data observed by the NASA Thermosphere Ionosphere Mesosphere Energetics Dynamics Solar EUV Experiment (TIMED/SEE). The datasets include thermosphere mass density measured by the Challenging Minisatellite Payload (CHAMP) satellite and derived from satellite drag data, thermosphere composition data measured by the NASA Thermosphere Ionosphere Mesosphere Energetics Dynamics Global UltraViolet Imager (TIMED/GUVI) and the NASA Global-scale Observations of the Limb and Disk (GOLD), and total electron content data from the Global Positioning System (GPS) network.


Date and time: 
Wednesday, January 29, 2020 - 2:00pm to 3:00pm