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arXiv · 2609.07839

Global 3D simulations of convection and dynamos in Red Giants

Carolina Ortiz-Rodríguez·Petri Käpylä·Juan Pablo Hidalgo·Dominik Schleicher·Robi Banerjee
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Abstract

Understanding the internal dynamics of red giants is essential for studying angular momentum transport and magnetic field generation during stellar evolution. We present three-dimensional magnetohydrodynamic simulations of a $1M_{\odot}$ red giant at the bottom of the red giant branch using a star-in-a-box setup with the Pencil Code, together with ongoing efforts to refine the numerical model. By varying the rotation rate, we explore different Rossby numbers and identify systematic changes in the convective dynamics and large-scale flows. As the rotation increases, convective motions become more anisotropic, showing clear signatures of rotational constraint and a shift in the dominant convective scales. These changes are accompanied by variations in the differential rotation profile, reflecting the redistribution of angular momentum within the convective envelope. The impact of rotation is also evident in the growth rate and saturation level of the magnetic field, indicating a strong dependence of dynamo efficiency on the underlying flow structure. Together, these results highlight the interplay between convection, rotation, and large-scale flows in shaping magnetic activity in red giant stars.

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Carolina Ortiz-Rodríguez, Petri Käpylä, Juan Pablo Hidalgo, Dominik Schleicher, Robi Banerjee. 2026-09-07. Global 3D simulations of convection and dynamos in Red Giants. https://doi.org/10.5281/zenodo.22197310

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