Toward Improving IonosphereThermosphere Forecasts GSFC Workshop on Impacts

Toward Improving Ionosphere-Thermosphere Forecasts GSFC Workshop on Impacts of Intermediate Time Scale SSI Variability 9 December 2018 Eric Sutton Rachel Hock-Mysliwiec Carl Henney Ed Thiemann Image Credit: NASA LASP

Wavelength Binning Scheme for TIE -GCM • Both the solar spectrum and the O, O 2, and N 2 cross-sections are highly variable in the EUV/FUV. • In order to compute I-T models efficiently, a reasonable number of wavelength bins need to be used. • One of the most common binning schemes is the “Stan Bands”: – Accounts the structure of the cross-sections (several overlapping bans) – Reflects the source region of solar emissions (like lines are binned together) – Accounts for the availability of solar data High-resolution solar EUV spectra and high-resolution atmospheric cross-sections showing the wavelength variability (from Solomon and Qian, 2005).

Solar Input into TIE-GCM Solar input proxy model in TIE-GCM using F 10. 7: 0. 05 -0. 8 nm: GOES XRS 0. 8 -1. 8 nm: From various rockets 1. 8 -5 nm: Hinteregger model (SC 21 REFW based on AE-E) 5 -105 nm: EUVAC model (F 74113 reference spectrum + variability from AE-E and rockets) 105 -175 nm: Woods and Rottman model (UARS SOLSTICE + 1994 rocket)

Comparison of F 10. 7 -proxy Model to Recent Observations Correlation coefficient reflects how well short-term variability is reproduced by F 10. 7 Current coefficients (black lines) and what they would be if calculated with recent observations (colored circles).

Band 7: 15. 5 -22. 4 nm The SDO/MEGS data reproduces the proxy model coefficients very well.

Band 26: Lyman α 121. 56 nm The composite uses F 10. 7 to fill in gaps Similar slope different offset reflects a change is absolute calibration with recent instruments

Band 30: 135. 0 -140. 0 nm

Data/Model Comparison F 10. 7 proxy-driven vs. EUV/FUV observation-driven F 10. 7 Proxy Driven Case Studies: • • 2002: 7 – 27 Oct. 2008: 25 Mar. – 14 Apr. 2014: 15 Jan. – 5 Feb. 2015: 20 Feb. – 12 Mar. IGS Network Observed TEC Driven w/ measured spectrum

Data/Model Comparison F 10. 7 proxy-driven vs. EUV/FUV observation-driven Case Studies: • • 2002: 7 – 27 Oct. 0 2008: 25 Mar. – 14 Apr. 2014: 15 Jan. – 5 Feb. 2015: 20 Feb. – 12 Mar. 0 IGS Network Observed TEC 0 0

Data/Model Comparison F 10. 7 proxy-driven vs. EUV/FUV observation-driven TIMED/SEE spectrum deposits more energy: • Texo enhanced by ~40 -50 K • F-peak enhanced by ~20% • ~10% depletion in the E-Region F-region features: • Profiles are nearly the same at 200 km • Changes accumulate moving toward the F-peak (i. e. chemical production vs. loss) • Differences at F-peak very nearly map upwards (i. e. no huge changes in plasma temperature) Root causes: • Direct: via increased photoionization/ photoelectron impact? • Indirect: via change in chemistry due to shift in neutral O/N 2 profile?

Observed vs. Estimated EUV/FUV Variability Without With Driver. Estimation Solar Flux Geomagnetic Kp Index (Upper Envelope) IRIDEA: Iterative Re-Initialization, Driver Estimation, and Assimilation

Investigating Density Variability using Solar Occultations • • EUV solar occultations can probe neutral density from ~130400 km PROBA 2 LYRA can be used to retrieve N 2+O sum (Thiemann+ SW 15 2017) – Data publicly available online through the PROBA 2 Science Center • Comparison of densities during strong solar rotation show that a 10% EUV increase in 5 days. . . – – • Increases 350 km density by 40% (30%) at dawn (dusk). Relative Enhancement less at lower altitudes Slight Lag time for thermospheric response Additional variability caused by geomagnetic effects 25% EUV decrease and in 5 days along with quiet geomagnetic conditions decreases dusk (dawn) density by 35% (53%) at 350 km.

Future EUV Occultation Instruments LASP Built Photometer Suitable for EUV Occultations • • Small Size of EUV occultation photometers make it attractive candidate for Cube. Sats and Flights of Opportunity to characterize and/or monitor thermospheric density, composition and temperature. One example is the ~3 U Occultation Wave Limb Sounder (OWLS) Instrument for characterizing thermosphere’s response to gravity waves by measuring. . . – Gravity wave vertical wavelength and potential energy – Thermospheric density and temperature • OWLS has secured a flight of opportunity on the Singapore built INSPIRESat 3 18 U Microsatellite, and instrument development has been proposed to HTIDe. S 2018.

What is important for 1 -3 day predictions of the I-T? 1. Long-term differences in EUV/FUV irradiance – How do we handle calibration of solar irradiance measurements and tuning of the models? 2. Differences on solar rotational time-scales – F 10. 7 -based model forces all the bands to vary “in-phase” which is not always accurate 3. Sub-daily measurements – What is the impact of using higher cadence versus a daily measurement?

Questions? 15