MAGNETIC CYCLES IN A DYNAMO SIMULATION OF FULLY CONVECTIVE M-STAR PROXIMA CENTAURI

被引:48
作者
Yadav, Rakesh K. [1 ]
Christensen, Ulrich R. [2 ]
Wolk, Scott J. [1 ]
Poppenhaeger, Katja [1 ,3 ]
机构
[1] Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA
[2] Max Planck Inst Sonnensyst Forsch, Justus Von Liebig Weg 3, D-37077 Gottingen, Germany
[3] Queens Univ Belfast, Astrophys Res Ctr, Belfast BT7 1NN, Antrim, North Ireland
基金
美国国家科学基金会;
关键词
dynamo; methods: numerical; stars: individual (Proxima Cen); stars: interiors; stars: low-mass; stars: magnetic field; M-DWARF STARS; SPHERICAL-SHELL DYNAMOS; ROTATION PERIODS; WAVE-PROPAGATION; DRIVEN DYNAMOS; ZONAL FLOW; FIELD; PLANETS; STRATIFICATION; SATURATION;
D O I
10.3847/2041-8213/833/2/L28
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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. 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 that 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.
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页数:6
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