Tidal dynamo in solar-like close binary stars

TL;DR

This paper proposes that large-scale tidal flows, rather than thermal convection, can induce magnetic dynamo action in close binary stars, with magnetic energy scaling with the cube of orbital frequency.

Contribution

It introduces a novel dynamo mechanism driven by tidal flows in close binary stars, supported by theoretical estimates linking tidal flow to magnetic energy.

Findings

Magnetic energy is proportional to the cube of orbital frequency.

Tidal flows can be comparable or stronger than convective flows in close binaries.

The proposed mechanism can be tested with future observations and simulations.

Abstract

Thermal convection is commonly believed to be the energy source of stellar or planetary dynamo. In this short paper we provide another possibility, namely large-scale tidal flow. In close binary stars, say, solar-like stars with orbital period at 2 or 3 days, large-scale tidal flow is comparable to or even stronger than convective flow, and it can induce magnetic dynamo action. Based on dynamo equation and tidal theory we estimate the magnetic energy induced by large-scale tidal flow, which is proportional to the cube of orbital frequency. Our estimation can be tested by the future spectropolarimetric observations and numerical simulations for close binary stars.