SH007-01
Global-Scale Convective Flows: Window into the Dynamo
Monday, 7 December 2020: 20:30
Virtual
Nicholas Andrew Featherstone, University of Colorado Boulder, Applied Mathematics, Boulder, CO, United States; Southwest Research Institute Boulder, Boulder, CO, United States, Bradley Hindman, University of Colorado Boulder, JILA & Applied Mathematics, Boulder, CO, United States, Keith A Julien, Univ of Colorado--Boulder, Applied Mathematics, Boulder, CO, United States and Geoffrey M Vasil, University of Sydney, Sydney, Australia
Abstract:
Outstanding gaps persist in our understanding of the solar dynamo. Numerous, and potentially viable descriptions of this physical system now exist, but not one has been convincingly tied to dynamics at work in the Sun, and for good reason. Convection, an indispensable component of the dynamo, occurs in the presence of rotation, and that rotation inevitably impacts key components of the solar dynamo. The Sun's differential rotation, its meridional circulation, and its turbulent EMF must all ultimately derive from the interaction of rotation and convection, and the strength of that interaction hinges crucially on the structure of the convective velocity spectrum. Precisely how convective flow strength varies with depth and across spatial scale remains largely unquantified, both observationally and theoretically, throughout the bulk of the convection zone. This situation in turn prevents us from assessing the relative likelihood of competing, or possibly complementary, dynamo paradigms.
Isolating those dynamo mechanisms that manifest in the Sun will first require obtaining deeper knowledge of its underlying convective motions, and that endeavor increasingly relies on a combination of observation, theory, and intuition from numerical modeling to yield new insight. In this presentation, we provide a brief summary of how convective structure relates to convective flow speed and rotation rate, and how that structure in turn relates to the propensity of a star for sustaining a dynamo. We will then discuss how several facets of the convection zone, from supergranulation, to the prograde rotation of its equator, to the possible multi-cellular nature of its meridional circulation are interrelated and provide clues concerning the structure and amplitude of deep solar convection. We conclude by presenting new theoretical results that contribute to this ongoing discussion and which suggest that a spatial scale of O(30 Mm) is the likely dominant spatial scale of deep solar convection.
