National Aeronautics and Space Administration

Living With A Star

Targeted Research and Technology

Helioseismology of the Solar Dynamo

ROSES ID: NNH08ZDA001N      Selection Year: 2009      

Program Element: Focused Science Topic

Principal Investigator: Martin Woodard

Affiliation(s): Northwest Research Associates, Inc.

Project Member(s):
Wachter, Richard Co-I Stanford University
Braun, Douglas C Co-I NorthWest Research Associates, Inc.
Crouch, Ashley D Co-I NorthWest Research Associates
Schou, Jesper Co-I Max Planck Institute for Solar System Research
Birch, Aaron C Co-I Max Planck Institute for Solar System Research


We propose to improve current measurements of solar meridional and zonal flows

by analyzing the nearly continuous 12-year sequence of Dopplergrams from the

SOHO/MDI medium-l helioseismology program.

The analysis technique we will use is based on measuring a mode-leakage

matrix which is sensitive to the distortion of mode eigenfunctions by flows

Significant effort will be devoted to identifying, understanding, and

modeling instrumental error.

We are proposing (1) to model and correct for instrumental and

radiative transfer effects, (2) to model the theoretical effect of differential

rotation and meridional circulation on the leakage matrix, (3) to develop

and verify codes to fit the leakage model to helioseismic data, and to

run the fitting codes on MDI data and, (4) to invert measurements of the

leakage matrix for meridional and zonal flows.

The resulting measurements of deep flows are anticipated to be accurate

enough to impact our understanding of the solar dynamo, as meridional flow

is a critical component of flux-transport dynamos. In addition, the

leakage matrix measurements we will carry out will be useful to other

areas of helioseismology.

The goals and measures of success of Focused Science Topic (a) -- "Measure

the properties of the solar dynamo that affect solar irradiance and active

region generation" -- include "improved measurements of critical subsurface

flows, including the expected deep meridional flow." The detection of sub-

surface meridional flow promises to facilitate our understanding of, and

perhaps predict, the generation, emergence, and evolution of magnetic

regions. This research is therefore critical to the TR&T Focused Science

Topic and NASA's Strategic Subgoal 3B through Research Objective 3B.1:

"Understand the fundamental physical processes of the space environment from

the Sun to Earth .. ", which addresses NASA's Science Question, "How and why

does the Sun vary?" from Strategic Subgoal 3B.


Performance YearReferenceInvestigation TypeActions
1Woodard, M. F.; (2009), Seismic Detection of Solar Mesogra...
not set
1Woodard, M.; Schou, J.; Birch, A. C.; Larson, T. P....
not set
1Woodard, M.; (2014), Detectability of Large-Scale Solar Sub...
not set


Performance YearReferenceActions
1Woodard, Martin F.; (2009), Helioseismic Detection of Mesogr...
1Schou, Jesper; Woodard, M. F.; Birch, A. C.; (2009), ...
1Woodard, M. F.; (2009), Helioseismic Measurement of Large-Sc...
1Schou, Jesper; Woodard, M. F.; Larson, T. P.; (2012),...

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