Targeted Research and Technology Topic Measure the Properties

Targeted Research and Technology Topic: “Measure the Properties of the Solar Dynamo that Affect Solar Irradiance and Active Region Generation” F. Busse, V. Pipkin (UCLA), P. Foukal (Heliophysics, Inc. ), A. Kosovichev, S. Ilonidis, I. Kitiashvili, K. Nagashima, K. Parchevsky, J. Zhao (Stanford), Y-M. Wang, N. Sheeley (NRL), M. Woodard, A. Birch, D. Braun, A. Crouch, T. Larson, J. Schou (NWRA/Stanford).

The five topics addressed by our Focus Team: • “Using Dynamo and Data Assimilation Methods for Modelling and Forecasting Properties of Solar Cycles” (UCLA) • “Facular Studies to Understand Solar Dynamo and Irradiance Behavior”(Heliophysics, Inc. ) • “Determination of the Large – Scale and Meridional Flows in the Deep Convection Zone by Time-Distance Helioseismology” (Stanford) • “ The Sun’s Polar Fields and the Dynamo” (NRL) • “Helioseismology of the Solar Dynamo” (NWRA/Stanford) Principal meetings of our Focus Team: Boulder, CO (June 2009); Miami, FL (June 2010); Las Cruces, NM ( June 2011).

Our Focus Team’s work since mid - 2009 has produced the following main advances: • An explanation of spot - cycle asymmetry, and of Waldmeier’s relations, based on magnetic helicity in the sub – photospheric shear layer, using a 2 - D dynamo model. • An explanation of the longitudinal clustering of active regions based on a new non – axisymmetric regime found in 3 – D dynamo simulations. • Verification of sub -surface meridional flow estimates, from sensitivity of cross spectra of helioseismic velocity fields, to meridional flow depth. • Improved meridional flow measurements using 3 -D simulations based on time – distance helioseismology and Fourier – Legendre decomposition techniques, applied to SDO/HMI data. • An explanation of the North – South asymmetry of the coronal streamer belt, in terms of the N-S asymmetry of sunspot numbers, using a 2 – D flux transport model. • An improved record of 20 th century solar magnetic fields, based on Carrington maps of chromospheric intensity produced from the digitized Mt Wilson Ca K spectroheliograms. • Discovery of the larger radiative losses per unit area of smaller faculae, which increases the likelihood of climatically significant 17 th century solar dimming. • An improved solar irradiance reconstruction showing greater 11 – yr variation between 1925 - 45, and ruling out claims for strong, 20 th century solar radiative forcing of climate.