2016/10/09 by Rakesh K. Yadav, Ulrich R. Christensen, Scott J. Wolk +1 · 1 voice · 62 citations
Engineering · Physics and Astronomy · #Astronomy and Astrophysical Research #Convection #Convection zone #Differential rotation #Dynamo #Dynamo theory #Exoplanet #Magnetic field #Space Technology and Applications #Stars #Stellar, planetary, and galactic studies #astro-ph.SR
paper · pdf · open access · doi:10.3847/2041-8213/833/2/l28
published in The Astrophysical Journal Letters 833(2), L28 (IOP Publishing) · 8 pages, 4 figures, double column; Accepted in ApJ Letters
openalex created_date 2016/10/21 · arxiv created 2016/12/01 · openalex publication_date 2016/12/19 · arxiv updated 2016/12/28 · openalex updated_date 2026/08/05
The recent discovery of an Earth-like exoplanet around Proxima Centauri has shined a spot light on slowly rotating fully convective M-stars. When such stars rotate rapidly (period \lesssim 20 days), they are known to generate very high levels of activity that is powered by a magnetic field much stronger than the solar magnetic field. Recent theoretical efforts are beginning to understand the dynamo process that generates such strong magnetic fields. However, the observational and theoretical landscape remains relatively uncharted for fully convective M-stars that rotate slowly. Here we present an anelastic dynamo simulation designed to mimic some of the physical characteristics of Proxima Centauri, a representative case for slowly rotating fully convective M-stars. The rotating convection spontaneously generates differential rotation in the convection zone which drives coherent magnetic cycles where the axisymmetric magnetic field repeatedly changes polarity at all latitudes as time progress. The typical length of the `activity' cycle in the simulation is about nine years, in good agreement with the recently proposed activity cycle length of about seven years for Proxima Centauri. Comparing our results with earlier work, we hypothesis that the dynamo mechanism undergoes a fundamental change in nature as fully convective stars spin down with age.