photoelectrons as a tool to evaluate solar euv and xuv model irradiance spectra on solar rotation...

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

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.


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

Photoelectron Observations

FAST observations available from January 1, 1997 to April 30, 2009

ePOP observations available in 2012?


Photoelectron Observations

September 14 to December 31, 2006Peterson, MURI, Boulder, 2011

Primarily northern hemisphere before Nov. 7.

Primarily near the terminator after Nov. 7

Solar irradiance models and TIMED/SEE observations

*

Comparison of observed and modeled photoelectron spectra

for a one minute interval


Comparisons of observed and modeled photoelectron power density

for a one minute interval


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


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


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

Center-limb brightening and soft X-ray flux variations are not in any of

the irradiance models


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


FLIP GLOW Code Differences


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

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.


Extra Slides


FLIP GLOW Code Differences


GLOW code produces ~30% lower photoelectron fluxes above ~ 20 nm

photoelectrons as a tool to evaluate solar euv and xuv model irradiance spectra on solar rotation...

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