National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Understanding the sources of the solar spectral and total irradiance variability and forecasting tools

ROSES ID: NNH06ZDA001N      Selection Year: 2007      

Program Element: Focused Science Topic

Principal Investigator: John Fontenla

Affiliation(s): University of Colorado

Project Member(s):
Gonzalez Hernandez, Irene Collaborator National Solar Observatory
Lindsey, Charles Allan Collaborator NorthWest Research Associates, Inc.

Summary:

We propose new research into the physical origins of the UV solar spectral irradiance variations and their contribution to the total. This research will expand tools we have developed to relate the visible and infrared solar spectral irradiance variations to features observed on the solar disk, namely active regions and network, through semi-empirical atmospheric models constructed to explain their spectra. Our approach is based on the physical processes of non-Local Thermodynamic Equilibrium (NLTE) radiative transfer and observational diagnostics of physical parameters characterizing the solar atmosphere. This approach uses high-quality solar images at key wavelengths together with our published semi-empirical models, and has been very successful in reproducing observed spectral irradiance variations for lambda>400 nm during the last few years.

We propose here extending our techniques to the UV solar spectral irradiance, in the range 100-400 nm, and developing forecasting tools better than the currently available proxy methods. This wavelength range displays important variability and is critical for photochemical reactions and heating of the Earth s upper atmosphere and those of other planets.

By using image analysis and spectral irradiance synthesis in combination with far-side helioseismic imaging and data analysis of Lyman alpha backscattering from the interplanetary medium (observed by the SOHO/SWAN instrument) we will be able to infer the radiation spectra in any direction and forecast the solar irradiance based on the knowledge of the distribution and radiative characteristics of the active regions. Our research can produce very high spectral resolution (up to / ~106) and greatly improved predictions of UV spectral irradiance that can be used modeling the Earth s atmosphere .

This research has important applications for understanding long-term spectral and total irradiance trends, for connecting solar dynamo and magnetic field studies with the Sun's radiative output, and for short-term (~2 weeks) forecasting of the Earth radiative environment that is critical for predicting satellite drag.

Publications:

Performance YearReferenceInvestigation TypeActions
1Fontenla, J., Balasubramaniam, K.S., & Harder, J. 2007, "Sem...
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1Fontenla, J., Curdt, W., Avrett, E.H., & Harder, J. 2007, "...
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1Fontenla, J.M., Peterson, W.K., & Harder, J. 2008, "Chromos...
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1Platnick, S. & Fontenla, J.M. 2008, "Model Calculations of ...
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1Fontenla, J. M.; Curdt, W.; Haberreiter, M.; Harder,Â...
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Presentations:

Performance YearReferenceActions
1Fontenla, Juan; Haberreiter, Margit; Quemerais, E.; (20...
1Haberreiter, M.; Fontenla, J.; Gonzalez-Hernandez, I.;Â...
1Fontenla, Juan; Haberreiter, M.; Harder, J.; (2009), To...
1Peterson, W. K.; Woods, T. N.; Fontenla, J. M.; Ric...
1Peterson, W. K.; Woods, T. N.; Fontenla, J. M.; Ric...

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