# Cycle period, differential rotation and meridional flow for early M dwarf stars

Source: [Cycle period, differential rotation and meridional flow for early M dwarf stars](<https://www.sota2.com/research/paper/68fa391c1e209131ce8bfe97>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-27T03:55:31.143Z

Authors: M. K\\"uker, G. R\\"udiger, K. Ol\\'ah, K. G. Strassmeier

Published: 2018-04-09T11:49:56.000Z

## Abstract

Recent observations suggest the existence of two characteristic cycle times for early-type M stars dependent on the rotation period. They are of order one year for the fast rotators ($P\_{\\rm rot}\<1$ day) and of order 4 years for the slower rotators. Additionally, the equator-to-pole differences of the rotation rates with $\\delta\\Omega$ up to 0.03 rad d$^{-1}$ are known from Kepler data for the fast-rotating stars. These values are well-reproduced by the theory of large-scale flows in rotating convection zones on the basis of the $\\Lambda$ effect. The resulting amplitudes $u^{\\rm m}$ of the bottom value of the meridional circulation allows the calculation of the travel time from pole to equator at the base of the convection zone of early-type M stars. These travel times strongly increase with rotation period and they always exceed the observed cycle periods. Therefore, the operation of an advection-dominated dynamo in early M dwarfs, where the travel time must always be shorter than the cycle period, is not confirmed by our model nor the data.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/1804.02925>)

[PDF](<https://arxiv.org/pdf/1804.02925.pdf>)