Contributed talk: Helioseismic imaging of supergranulation

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• Chris Hanson (New York University)
• Tuesday 29 November 2022, 11:45-12:15
• Seminar Room 1, Newton Institute.

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DY2W03 - Modeling, observing and understanding flows and magnetic fields in the Earth's core and in the Sun

The Sun has a convection conundrum. The outer 30% of the solar interior is known as the convection zone, where in the simplistic picture: hot material from the base rises, cools at the near surface and returns back into the interior. Theory and numerical calculations stipulate the existence of a multi-scale regime of convection; where horizontally large scale diverging flows dredge up hot material from the deep interior and smaller scale convection overturns material in the near-surface. In between these extreme scales should exist a spectrum of convective features. The conundrum is that the existence of large scale convection (_{100Mm) has eluded observers, and only two scales of convection exist: granulation (}1Mm) and supergranulation (36Mm). While the properties of granulation are well replicated by numerical simulations, not much is known about the depth structure of supergranulation and what role this apparently preferred flow scale plays in solar convection. Using 3 years of high resolution spacecraft data and local helioseismic mode coupling techniques, we construct average supergranules ranging from 32 to 45~Mm in horizontal scale. Through inversion methods, we obtain the depth structure of these flows from the helioseismic data. We also determine the surface structure (sound speed, density and magnetic field). In this talk I will present our results and discuss their implications for solar convection. Co-Authors: Srijan Das, Prasad Mani, Shravan Hanasoge, Katepalli Sreenivasan

This talk is part of the Isaac Newton Institute Seminar Series series.

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