RUI: An Investigation of the Solar Torsional Oscillations

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The investigators at this undergraduate institution will study the mechanisms that drive solar torsional oscillations. The rotational perturbation exhibits a time-dependent pattern which links it to the Sun's magnetic activity cycle. Comparisons of the torsional pattern with the cycle-related patterns of meridional flow and magnetic field suggest that it is actually made up of three separate phenomena, and that each is the result of Coriolis forces. These three are: (1) a polar spin-up associated with poleward meridional flow to a downdraft at the poles at the time of polar field reversal; (2) a migrating zone of enhanced shear associated with meridional flows to a downdraft overlying the toroidal field band that gives rise to the active regions of the cycle; and (3) an equatorial slowing due to an updraft at the equator that feeds a poleward meridional flow. The principal investigator and students will examine these and other scenarios that have been proposed through the analysis of data taken in two spectral lines at Mount Wilson since 1986 and with data taken in the GONG and SOHO programs. This investigation will probe the torsional pattern's longitudinal and radial structure, and compare it with the structures in the patterns of meridional motion and magnetic field. The investigators will also examine the methods used to reveal the pattern and address the possibility of making solar cycle predictions.