National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Understanding solar EUV Irradiance (EUVI) observed over the 11-year solar cycle

ROSES ID: NNH07ZDA001N      Selection Year: 2008      

Program Element: Focused Science Topic

Principal Investigator: Dennis Martinez-Galarce

Affiliation(s): Lockheed Martin Advanced Technology Center

Project Member(s):
Slater, Gregory Lee Co-I Lockheed Martin
De Pontieu, Bart Collaborator Lockheed Martin Solar & Astrophysics Lab
Boerner, Paul Collaborator Lockheed Martin
McIntosh, Scott William Collaborator National Center for Atmospheric Research


The principal focus of the proposed 3-year investigation is to empirically determine the solar EUV spectral irradiance (EUVI) measured by the SoHO-EIT instrument over its lifespan of operation covering a full solar cycle. Using this dataset, the thrust of the investigation will be threefold: 1) to determine the full-disk EUVI in each of the four EIT wavebands (171, 195, 284 and 304 Ö); 2) to quantify the percent coverage of active versus quiescent region emission (over the full disk) in each waveband; and 3) to study the diffusely unresolved component of EUV emission emanating from quiet regions recorded in EIT, CDS and TRACE spectroheliograms.

Solar EUVI is known to be the primary source of energy that drives the photochemistry, ionization and heating of the Earth's upper atmosphere above ~ 100 km, contributing to Earth's delicate heating balance and therefore its climate. Changes in atmospheric density caused by EUVI (e.g. a thickening of the ionosphere) affect space-based satellites by "dragging" them to lower orbits and lowering their expected operational lifetimes. A priori knowledge of EUVI variation in conjunction with satellite tracking models will assist satellite operators in countering such affects. Accurate determination of EUVI is also useful for climate and geospace modelers wishing to improve their prediction of solar EUVI effects on the Earth's thermosphere, ionosphere and atmospheric composition and how it affects and modulates Earth climate (e.g. EUV models NRLEUV2, HFG, EUVAC and SOLAR2000).

The source of EUVI is known to be the solar atmosphere. To understand long term variability, we will test state-of-the-art models of coronal funnels. These structures are open magnetic field regions rooted in the supergranular network, expanding outward into the corona and solar wind and produce a sizeable component of the EUV and soft X-rays from quiet regions. Funnels are also believed to be the source of the fast solar wind coming from coronal holes. Using CDS and TRACE observations in conjunction with simultaneously recorded EIT data we will measure areal expansion of funnels at different temperatures, and over a select number of observations throughout the solar cycle to understand the morphological transformation the EUV Sun traverses over this period.

The knowledge gained will be especially important to Earth climate modelers wanting to understand how EUVI affects Earth's climate (vis- -vis global warming) as well as give solar physicists a better understanding of the heating mechanisms that produce solar EUV radiation and those that generate the solar wind. The results will also be important to geospace modelers to help predict EUVI effects on space weather and its impact to human-engineered systems.

The tools developed in this study will also be useful for analysis of STEREO, Solar-B and SDO-AIA observations.


Performance YearReferenceInvestigation TypeActions
1Martínez-Galarce, Dennis S.; Boerner, Paul; Soufli, R...
not set
1Martínez-Galarce, Dennis; Harvey, James; Bruner, Marilyn; L...
not set


Performance YearReferenceActions
1Boerner, P.; Martinez-Galarce, D.; de Pontieu, B.; So...
1Martinez-Galarce, D. S.; Slater, G. L.; Mcintosh, S. W.; (20...
1Martinez-Galarce, Dennis S.; Boerner, P.; Stern, R.; ...

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