Magnetic Quenching of Turbulent Diffusivity: Reconciling Mixing-length Theory Estimates with Kinematic Dynamo Models of the Solar Cycle - Astrophysics > Solar and Stellar AstrophysicsReportar como inadecuado




Magnetic Quenching of Turbulent Diffusivity: Reconciling Mixing-length Theory Estimates with Kinematic Dynamo Models of the Solar Cycle - Astrophysics > Solar and Stellar Astrophysics - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

Abstract: The turbulent magnetic diffusivity in the solar convection zone is one of themost poorly constrained ingredients of mean-field dynamo models. This lack ofconstraint has previously led to controversy regarding the most appropriate setof parameters, as different assumptions on the value of turbulent diffusivitylead to radically different solar cycle predictions. Typically, the dynamocommunity uses double step diffusivity profiles characterized by low values ofdiffusivity in the bulk of the convection zone. However, these low diffusivityvalues are not consistent with theoretical estimates based on mixing-lengththeory - which suggest much higher values for turbulent diffusivity. To makematters worse, kinematic dynamo simulations cannot yield sustainable magneticcycles using these theoretical estimates. In this work we show that magneticcycles become viable if we combine the theoretically estimated diffusivityprofile with magnetic quenching of the diffusivity. Furthermore, we find thatthe main features of this solution can be reproduced by a dynamo simulationusing a prescribed kinematic diffusivity profile that is based on thespatiotemporal geometric-average of the dynamically quenched diffusivity. Here,we provide an analytic fit to the dynamically quenched diffusivity profile,which can be used in kinematic dynamo simulations. Having successfullyreconciled the mixing-length theory estimated diffusivity profile withkinematic dynamo models, we argue that they remain a viable tool forunderstanding the solar magnetic cycle.



Autor: Andrés Muñoz-Jaramillo, Dibyendu Nandy, Petrus C. H. Martens

Fuente: https://arxiv.org/



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