1. Photoelectrons as a tool to evaluate Solar EUV and XUV model irradiance spectra on Solar rotation time scales W.K. Peterson 1, T.N. Woods 1, J.M. Fontenla 1, P.G. Richards 2, W.K. Tobiska 3, S.C. Solomon 4, and H.P. Warren 5 1 LASP/CU, 2 George Mason, 3 Utah State, 4 HAO/NCAR, 5 NRL Peterson, MURI, Boulder, 2011

2. Outline How do we compare photoelectrons and irradiance models? Some details of the comparisons: Conclusions: –None of the Solar irradiance models investigated captures the variation of Solar energy input into the thermosphere on Solar rotation time scales. –All of the Solar irradiance models investigated adequately reproduce the average Solar energy input to the thermosphere over the 109 day interval examined. –There are systematic differences between photoelectron spectra calculated using the FLIP and GLOW codes, but the differences are comparable to observational uncertainties. Peterson, MURI, Boulder, 2011

3. Uncertainties in solar Irradiances create uncertainties in thermospheric models Altitude-wavelength dependence of energy deposition from solar irradiance in units of Log 10 (Wm -4 ) From Solomon and Qian 2005 Solar minimum conditions Color Bar: Log 10 (Wm -4 ) Peterson, MURI, Boulder, 2011

4. Photoelectron Observations FAST observations available from January 1, 1997 to April 30, 2009 ePOP observations available in 2012? Peterson, MURI, Boulder, 2011

5. Photoelectron Observations September 14 to December 31, 2006 Peterson, MURI, Boulder, 2011 Primarily northern hemisphere before Nov. 7. Primarily near the terminator after Nov. 7

6. Solar irradiance models and TIMED/SEE observations *    

7. Comparison of observed and modeled photoelectron spectra for a one minute interval Peterson, MURI, Boulder, 2011

8. Comparisons of observed and modeled photoelectron power density for a one minute interval Peterson, MURI, Boulder, 2011 Observations solid line +/- 20% dotted line Photoelectron power density is the integral of the photoelectron energy flux over the 2-45 nm equivalent wavelength range expressed in Watts per m 2 On average 1.7% of the modeled irradiance power in the 2-45 nm band is seen in the photoelectron power density

9. Peterson, MURI, Boulder, 2011 Photoelectron observations in banded power density format Photoelectron power density in 5 bands (W/m 2 ) ( Observations – 109 day average ) / 109 day average Center-limb brightening from an extended coronal source Soft X ray flux unrelated to F 10.7 or SPRM model areas

10. Peterson, MURI, Boulder, 2011 Comparisons of observed and modeled photoelectron power density in 5 bands for 109 days in late 2006 Observation - Model / Model RED: Model > 50% Low GREEN: Model = Obs BLACK: No data or 50% high Center-limb brightening and soft X-ray flux variations are not in any of the irradiance models

11. Peterson, MURI, Boulder, 2011

12. All irradiance models reproduce average observed photoelectron power density Power Density in W/m 2 Grey indicates value is outside +/- 20% observational uncertainty Red indicates value is outside +/- 40% of the observed value FLIP/HEUVAC 6 bands within +/- 20% GLOW/HEUVAC, GLOW/FISM, GLOW/S2000, and SRPM driven by Rome observations with a coronal filling factor of 0.5 have 5 bands within +/-20% Average power density from Sept. 14 – Dec. 31 for 6 energy bands FLIPGLOW Peterson, MURI, Boulder, 2011

13. FLIP GLOW Code Differences Peterson, MURI, Boulder, 2011 GLOW code produces ~30% lower photoelectron fluxes above ~ 20 nm GLOW-FLIP difference is comparable to observational uncertainties (+/- 20%) 109 day average of model calculations

14. Conclusions None of the Solar irradiance models investigated captures the variation of Solar energy input to the thermosphere on Solar rotation time scales. All of the Solar irradiance models investigated adequately reproduce the average Solar energy input to the thermosphere over the 109 day interval examined. There are systematic differences between photoelectron spectra calculated using the FLIP and GLOW codes, but the differences are comparable to observational uncertainties. We need SDO/EVE observations to fully understand the temporal and spectral variations of solar irradiance.We need SDO/EVE observations to fully understand the temporal and spectral variations of solar irradiance. Peterson, MURI, Boulder, 2011

15. Extra Slides Peterson, MURI, Boulder, 2011

18. FLIP GLOW Code Differences Peterson, MURI, Boulder, 2011 GLOW code produces ~30% lower photoelectron fluxes above ~ 20 nm