The efficiency of convective tidal viscosity in close solar-type binaries

TL;DR

This paper investigates whether alternative models of stellar turbulent convection can resolve the long-standing discrepancy between observed and theoretical convective tidal viscosities in close solar-type binaries, showing promising improvements over traditional mixing length theory.

Contribution

The study applies a different turbulent convection model and analytic spectrum approximation, significantly increasing the predicted convective viscosity compared to MLT.

Findings

Efficiency increased by a factor of 30 compared to MLT

Discrepancy reduced from 1000 to 30 times

Supports alternative turbulence models for better tidal dissipation estimates

Abstract

The value of the effective convective viscosity, in the framework of the mixing length theory (MLT), is 2 orders of magnitude too small compared to that required by the observational data. Moreover, the reduction of the effective viscosity due to the fast time-variation of the tidal shear in short period binaries, increases the discrepancy to about three orders of magnitude. In this work, we examine the possibility that the apparent inefficiency of turbulent convection is merely a shortcoming of MLT approach. We employ a model for stellar turbulent convection (Canuto, Goldman & Mazzitelli 1996) and use an analytic approximation to the turbulent spectrum. The resulting efficiency is substantially increased; the discrepancy is a factor of 30 down from a factor of 1000. This encouraging result motivates an investigation of the full non-analytic solutions of the turbulent spectrum.