Explaining the Coexistence of Large-scale and Small-scale Magnetic Fields in Fully Convective Stars

Rakesh K. Yadav, Ulrich R. Christensen, Julien Morin, Thomas Gastine, Ansgar Reiners, Katja Poppenhaeger, Scott J. Wolk

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Despite the lack of a shear-rich tachocline region, low-mass fully convective (FC) stars are capable of generating strong magnetic fields, indicating that a dynamo mechanism fundamentally different from the solar dynamo is at work in these objects. We present a self-consistent three-dimensional model of magnetic field generation in low-mass FC stars. The model utilizes the anelastic magnetohydrodynamic equations to simulate compressible convection in a rotating sphere. A distributed dynamo working in the model spontaneously produces a dipole-dominated surface magnetic field of the observed strength. The interaction of this field with the turbulent convection in outer layers shreds it, producing small-scale fields that carry most of the magnetic flux. The Zeeman–Doppler-Imaging technique applied to synthetic spectropolarimetric data based on our model recovers most of the large-scale field. Our model simultaneously reproduces the morphology and magnitude of the large-scale field as well as the magnitude of the small-scale field observed on low-mass FC stars.
Original languageEnglish
Article numberL31
Number of pages6
JournalThe Astrophysical Journal Letters
Issue number2
Early online date04 Nov 2015
Publication statusPublished - 10 Nov 2015


  • dynamo
  • methods: numerical
  • stars: interiors
  • stars: low-mass
  • stars: magnetic field


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