W.K. Peterson 1 , J.M. Fontenla 1 , T.N. Woods 1 ,
description
Transcript of W.K. Peterson 1 , J.M. Fontenla 1 , T.N. Woods 1 ,
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Photoelectrons as a Tool to Evaluate Spectral and Temporal Variations of Solar EUV Irradiance Models
W.K. Peterson1, J.M. Fontenla1, T.N. Woods1,
P.G. Richards2, S.C. Solomon3, H.P. Warren4,
W.K. Tobiska5, and P.C. Chamberlin6
1LASP/CU, 2George Mason, 3NCAR/HAO,
4NRL, 5Utah State, 6NASA/GSFC
Peterson, MURI, October 2003
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Outline• Our method to compare photoelectron energy
observations and irradiance models • Comparisons of photoelectron energy spectra with those
predicted with two photoelectron production codes driven by the SPRM predictive model, and the FISM, HEUVAC, S2000, and NRL irradiance models
• Conclusions: – Surprisingly the empirical HEUVAC (EUVAC extended to 1 nm)
model produces photoelectron spectra that match the observations on daily and solar rotation period time scales.
– The SRPM prediction model matches the data as well or better than any of the data or index driven models.
– The physics based NRLEUV model does the poorest job of capturing the variation of energetic photoelectrons on a solar rotation time scale.
Peterson, MURI, October 2003
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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, October 2003
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Photoelectron Observations
FAST observations available from January 1, 1997 to April 30, 2009
ePOP observations available in late 2011
Peterson, MURI, October 2003
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Model Data Comparison
Average of 56 one-minute average spectra obtained for SZA < 90o
Two PE production codes
Seven Solar irradiance models
Peterson, MURI, October 2003
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Transformation to Equivalent Wavelength
Use a constant15 eV ionization potentialPeterson, MURI, October 2003
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Relative DifferenceObservation - Model / Model
as a Function of the Wavelength Equivalent of the Photoelectron Energy
S/N inadequate below ~3 nm (> 385 eV)
Above ~16 nm differences are less than +/- 50%
Above ~30 nm slight differences in PE’s predicted from the GLOW and FLIP models.
Both the GLOW and FLIP codes showTIMDED/SEE irradiances systematicallylow below about 15 nm
Peterson, MURI, October 2003
* GLOW/HEUVAC best agrees with observations
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FAST Observations from August 31 to September 30 2005
Observed Photoelectron flux vs. Energy (eV)
Vs. Equivalent Wavelength (nm)
F10.7
KP
DST
Each line in the color spectrogram panels shows a daily average photoelectron energy spectra with the flux given by the color bars on the right.
Peterson, MURI, October 2003
F10.7
AP
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Differences between Observations and Model PE Energy Spectra over a Solar Rotation
HEUVAC
SPRM-Rome
FISM
S2000
NRLEUV
Photoelectron energy spectra produced using the empirical HEUVAC model agree best with Observations.
The SPRM predictive model does as well as the TIMED/SEE based FISM model
Peterson, MURI, October 2003
SPRM-MLSO
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Observation-Model Differences -2
FISM produces good agreement except for underestimating the PE fluxes between 5 and 15 nm
S2000 produces low fluxes below 15 nm and relatively good agreement above 15 nm.
NRLEUV systematically underestimates the photoelectron flux below 15 nm
RED: Model >200% LowGREEN: Model = ObservationsBLACK: No data
Peterson, MURI, October 2003
HEUVAC
SPRM-Rome
FISM
S2000
NRLEUV
SPRM-MLSO
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Solar Irradiance Models Differ at Many Wavelengths
HEUVAC Model Color Bar is Irradiance in w/m2
Relative Differences are(Model - HEUVAC) / HEUVAC
HEUVAC
FISM
S2000
NRLEUV
RED: Model >400% than HEUVACGreen: Model = HEUVAC
Irradiance models are qualitatively
different above and below
~27 nm Peterson, MURI, October 2003
SPRM-Rome
SPRM-MLSO
F10.7
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Irradiance Power above and below 27 nm
HEUVAC
FISM
S2000
NRLEUV
Lowest: NRLEUVHighest: HEUVAC/S2000
Lowest: HEUVAC/NRLHighest: SPRM
SPRM-Rome
SPRM-MLSO
Peterson, MURI, October 2003
Photoelectron spectra produced using HEUVAC agree best with data
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Irradiance Spectral Models
• HEUVAC model has by design has broad spectral structure (~1eV) above 27 nm
• To first order all models agree about the spectral shape below 27 nm
• The most significant differences between irradiance models are in the relative power above and below 27 nm.
HEUVAC
FISM
S2000
NRLEUV
SPRM-Rome
SPRM-MLSO
Peterson, MURI, October 2003
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Conclusions• Surprisingly the empirical HEUVAC (EUVAC extended
to 1 nm) model produces photoelectron spectra that best match the observations on daily and solar rotation period time scales.
• Fontenla’s SRPM prediction model matches the photoelectron data as well or better than any of the other data or index driven models investigated.
• The physics based NRLEUV model does the poorest job of capturing the variation of energetic photoelectrons on a solar rotation time scale.
• 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, COSPAR, 2010, C12-0018