Measured and Modeled Trends in
Solar Spectral Irradiance Variability in
the Visible and Infrared
Jerald Harder, Juan Fontenla, Mark Rast, Erik Richard, Thomas Woods
Laboratory for Atmospheric and Space Physics (LASP)
University of Colorado, Boulder Colorado USA
jerald harder@lasp colorado edu
jerald.harder@lasp.colorado.edu
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 1
Topic Outline
• The
The unexpected nature of solar spectral variability
unexpected nature of solar spectral variability
• Interpretation of variability in term of the Solar Radiation Physical Modeling (SRPM)
– Image decomposition using the Precision Photometric Solar Telescope (PSPT)
• Mauna Loa Solar Observatory
• Rome Observatory (courtesy of Ilaria Ermolli)
• Conclusions 2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 2
Instrument Overview
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Instrument Type: Féry Prism Spectrometer
Wavelength Range: 200‐2400 nm
g
g
Wavelength Resolution: 0.24‐34 nm
Detector: ESR, n‐p silicon, InGaAs
Absolute Accuracy: 2‐8%
Relative Accuracyy : >0.1%
Long‐term Accuracy: 0.015%/yr
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Field of View: 1.5x2.5˚ total
Pointing Accuracy/Knowledge: 0.016˚/0.008˚
g
y/
g
/
Mass: 21.9kg
Dimensions: 88 x 40 x 19 cm
Orbit Average Power : 17.5 W
Orbit Average Data Rate: 1.5 kbits/s
g
/
Redundancy: 2 Redundant Channels
λ = 2423
∫
E ( λ ) d λ ≈ 1324.6
1324 6 Wm −2
λ = 200
≈ 97.3% of TSI
J.W. Harder, G. Thuillier, E.C. Richard, S.W. Brown,
K.R. Lykke, M. Snow, W.E. McClintock, J.M. Fontenla,
T.N. Woods, P. Pilewskie, 'The SORCE SIM Solar
Spectrum:
p
Comparison
p
with Recent Observations' ,
Solar Physics, 263, Issue 1 (2010), pp 3,
doi:10.1007/s11207-010-9555-y
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 3
The unexpected nature of solar spectral variability 2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 4
Origin of the Offsetting Trends – a work in progress
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SIM observations consistent with an overall decrease in the temperature gradient in
the active ((magnetic)
g
) solar p
photosphere
p
Crossing point occurs in the solar atmospheric layers that are close to the Teff value
The photospheres crossing point occurs at a temperature roughly designed to match
the Topka et al. observations (ApJ, 484, 1997).
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 5
SRPM Modeling of SIM Observations
Solar models from:
Fontenla et al.,
ApJ, 707, 482-502 (2009)
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Root causes of solar variability originates in changes in the magnetic and thermal structure of the solar atmosphere. The SRPM combines solar feature information with physics‐based solar atmospheric spectral models at high spectral resolution to compute the emergent intensity spectrum.
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 6
SRPM Spectrum
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SRPM calculates the solar SRPM
l l t th
l
spectrum at full spectral resolution (already reduced here).
Spectrum is calculated for each
Spectrum is calculated for each model .
High resolution spectrum can be convolved to any resolution for comparison with observations.
SRPM brightness temperatures reflect the cross‐over point near Teff
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 7
PSPT Solar Feature Identification
Ca IIK
393.45 nm, 0.273 FWHM
Identify Active Regions
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Red Continuum
607.095 nm, 0.458 FWHM
Identify Umbra & Penumbra
SRPM Mask Image
Identify 7 solar Features
Feature area determined from intensity analysis of PSPT images Analysis done as a function of disk position
Analysis done as a function of disk position and time
Full disk Irradiance determined from disk position and emitted intensity from each p
y
atmospheric model
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 8
SRPM Decomposition of Solar Cycle changes 2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 9
Atmospheric Models Center‐to‐Limb Variability
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 10
Spectral Irradiance Differences from Solar Minimum
‘Quiet sun’ = 0.75B + 0.22D + 0.03F
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 11
Time Series Comparison of SIM to SRPM/PSPT
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 12
SIM Observations in Climate Models
MODTRAN™5 Radiative Transfer Algorithm
courtesy of Gail Anderson
AFRL / Space Vehicles Directorate,
Directorate Hanscom
AFB, MA 01731
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Studies are starting to address SIM observations in climate models:
– Cahalan et al., GRL, 2010 (GISS ModelE)
– Haigh et al., Nature, submitted March 2010
Haigh et al Nat re s bmitted March 2010
– Merkel et al., in preparation, (WACCM)
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 13
Conclusions
• The
The combined SIM, SRPM, and PSPT image analysis provide a combined SIM SRPM and PSPT image analysis provide a
effective method to analyze solar variability
– SIM indicates irradiance trends that are larger than solar modulation that co pe sate to p oduce t e S t e d.
compensate to produce the TSI trend.
– SRPM analysis is able to capture offsetting trends observed by SIM, but refinements are still needed.
– Active region evolution by itself is not sufficient to account for the observations suggestive of changes in the internetwork/network observations –
suggestive of changes in the internetwork/network
radiance.
• In‐depth Earth atmospheric modeling is progressing
– Both direct SIM observations and SRPM model output are applicable
Both direct SIM observations and SRPM model output are applicable
• The Future
– The SORCE data records will continue through extended mission pp
,
p
opportunities, and the TSIS mission will continue this process
– The SRPM is a very mature solar atmospheric model and refinements will continue
– At this point in time, we need to consider building a second generation space based PSPT imager that can provide radiometric information i e
space‐based PSPT imager that can provide radiometric information, i.e. replace the notion of contrast with an absolute pixel intensity.
2010 SORCE Science Meeting
Keystone Colorado, May 19, 2010
Measured and Modeled Trends in Solar Spectral Irradiance Variability
Harder ‐ 14