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Photoelectrons as a tool to evaluate Solar EUV and XUV model irradiance
spectra
on Solar rotation time scales
W.K. Peterson1, T.N. Woods1, J.M. Fontenla1, P.G. Richards2, W.K. Tobiska3, S.C. Solomon4,
and H.P. Warren5
1LASP/CU, 2George Mason, 3Utah State, 4HAO/NCAR, 5NRL
Peterson, MURI, Boulder, 2011
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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
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Uncertainties in solar Irradiances create uncertainties in thermospheric models
Altitude-wavelength dependence of energy deposition from solar irradiance in units of Log10(Wm-4)
From Solomon and Qian 2005
Solar minimum conditions
Color Bar: Log10(Wm-4) Peterson, MURI, Boulder, 2011
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Photoelectron Observations
FAST observations available from January 1, 1997 to April 30, 2009
ePOP observations available in 2012?
Peterson, MURI, Boulder, 2011
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Photoelectron Observations
September 14 to December 31, 2006Peterson, MURI, Boulder, 2011
Primarily northern hemisphere before Nov. 7.
Primarily near the terminator after Nov. 7
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Solar irradiance models and TIMED/SEE observations
*
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Comparison of observed and modeled photoelectron spectra
for a one minute interval
Peterson, MURI, Boulder, 2011
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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 m2
On average 1.7% of the modeled irradiance power in the 2-45 nm band is seen in the photoelectron power density
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Peterson, MURI, Boulder, 2011
Photoelectron observations in banded power density format
Photoelectron power density in 5 bands (W/m2)
( Observations – 109 day average ) / 109 day average
Center-limb brightening from an extended coronal source
Soft X ray flux unrelated to F10.7 or SPRM model areas
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Peterson, MURI, Boulder, 2011
Comparisons of observed and modeled photoelectron power density in 5 bands for 109 days in late 2006
Observation - Model / ModelRED: Model > 50% LowGREEN: Model = ObsBLACK: No data or 50% high
Center-limb brightening and soft X-ray flux variations are not in any of the irradiance models
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Center-limb brightening and soft X-ray flux variations are not in any of
the irradiance models
Peterson, MURI, Boulder, 2011
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All irradiance models reproduce average observed photoelectron power density
Power Density in W/m2
Grey indicates value is outside +/- 20% observational uncertaintyRed indicates value is outside +/- 40% of the observed valueFLIP/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 FLIP GLOW
Peterson, MURI, Boulder, 2011
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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
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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 We need SDO/EVE observations to fully understand the temporal and spectral variations of solar the temporal and spectral variations of solar irradiance.irradiance.
Peterson, MURI, Boulder, 2011
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Extra Slides
Peterson, MURI, Boulder, 2011
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Peterson, MURI, Boulder, 2011
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Peterson, MURI, Boulder, 2011
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FLIP GLOW Code Differences
Peterson, MURI, Boulder, 2011
GLOW code produces ~30% lower photoelectron fluxes above ~ 20 nm